I have 2 problem sums here:

Question 1
The ratio of pizzas to the nuber of burgers that were ordered for a party was in the ratio 5:1. After the delivery man had made a mistake, the ratio of the number pizzas to the number of burgers that were sent to the party was 1:1.
a) If the man had ordered less than 20 items, how many pixxas and burgers were sent to the party?

b)How many burgers were replaced with pizzas after the delivery man had arrived?

Question 2
A purse contained $5 and $2 notes in the ratio 2:3. Some $5 notes were taken out and exchanged for $2 notes. The ratio of the number of $5 notes to the number of $2 notes became 2:7.
a) What is the total value of money in the purse at the beginning?

b) How many $5 notes were exchanged with $2 notes?

Thanks,

The ratio of pizzas to the nuber of burgers that were ordered for a party was in the ratio 5:1. After the delivery man had made a mistake, the ratio of the number pizzas to the number of burgers that were sent to the party was 1:1.
a) If the man had ordered less than 20 items, how many pixxas and burgers were sent to the party?

b)How many burgers were replaced with pizzas after the delivery man had arrived?

This question is actually missing information as there is no way to link the beginning ratio to the ending ratio (and there is only one equation with two unknowns). The result is that it will allow me to have many solutions depending on the assumption(s) I choose.

For example, if I choose to use the LCM for both ratios (and assume that 1unit for 5:1 is the same as 1 part for 1:1). The difference in total units, between before and after, is 4units resulting in 1unit being 5. Then we have 5 pizzas and 5 burgers being delivered.

If I change 5:1 to 10:2 and 1:1 to 2:2, which I would normally be allowed to do, I still get the same answer. Which is good.

But where does it say 1unit is 1part?

If I use algebra I would get
order - 20 --> sent
5u + 1u - 20 --> 1p + 1p
6u - 2p --> 20
3u - p --> 10

You will see that there is not sufficient information to solve the question.

All that said, assuming that 1unit is equal to 1part:
a) 5 pizzas and 5 hamburgers
b) With the above assumption, there was no replacement. 5burgers were ordered and 5burgers were delivered. There was just a decrease in pizzas.

So, for this question I would check the information and if it's correct than move on to the next.

For question no 2

a) is it $48?
b) is it 2 $5?

Sorry for the late response. I've attached a sample of the working for this type of question. I don't quite understand the method though

This is the attachment.