3*y =3y
3y+6=21
3y=21-6=10
3y=10
Three times a certain number plus 6 is equal to twice the number plus 15. What is the number?
2 answers
x = number
Three times a certain number plus 6 is equal to twice the number plus 15, means:
3 x + 6 = 2 x + 15
Subtract 2x to both sides.
x + 6 = 15
Subtract 6 to both sides.
x = 9
The number is 9.
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Proof:
3 x + 6 = 2 x + 15
3 • 9 + 6 = 2 • 9 + 15
27 + 6 = 18 + 15
33 = 33
____________________
Three times a certain number plus 6 is equal to twice the number plus 15, means:
3 x + 6 = 2 x + 15
Subtract 2x to both sides.
x + 6 = 15
Subtract 6 to both sides.
x = 9
The number is 9.
____________________
Proof:
3 x + 6 = 2 x + 15
3 • 9 + 6 = 2 • 9 + 15
27 + 6 = 18 + 15
33 = 33
____________________