9514 1404 393
Answer:
y = 42
Step-by-step explanation:
Undo what is done to y.
y/7 +15 = 21 . . . . . . . . . . . . given
y/7 = 6 . . . . . . . . . . . . . . subtract 15 to undo the addition of 15
y = 42 . . . . . . . . . . . . multiply by 7 to undo the division by 7
