fatima plans to spend at least $15 and at most $20 on sketchpad and pencils. if she buys 2 sketch pads, how many pencils can she buy

Question

show all work please 

Answer 1

15 </= budgeted spending </=20

if 2 sketchpads cost $10, and pencils cost $1 each

then she can buy from 5 to 10 pencils

staying within her budget

if 2 sketchpads cost x dollars and pencils cost y dollars

then she can buy (15-x)/y to (20-x)/y pencils

plug in x=10, y=1 and she can buy from 5 to 10 pencils