Answer:
18
Step-by-step explanation:
12 and 15 are both dividable by 3 and 3 apart so if you subtract 21 by 3 than you get 18
Answer:
18 or 16.8
Step-by-step explanation:
if x=12 and y=15, this can be written as y=x+3 or y=1.25x
so your equation becomes x+3=21 or 1.25x=21
subtract 3 from both sides, or divide by 1.25
and you get x=18 or x=16.8
