Answer:
Step-by-step explanation:
4) A photograph costs $20, so the cost of x photographs is 20x.
Similarly, the cost of y prints is $25.
So the total cost is 20x+25y, and this has to be less than or equal to 400, so C.
5) just plug each pair in.
For example for the first option, x=5 and y=10, and since 20(5)+25(10)=100+250. which is less than or equal to 400, it works.
