Question

When 15 is added to 7 times a certain number, the result is equal to subtracting 3 from 10 times that number. Find the number?

Answer 1

The number is 6.

Explanation:

Let's call the unknown number x and set up a system of equations:
`7x + 15 = 10x - 3`

Subtract 7x from both sides.
`15 = 3x - 3`

Add 3 to both sides.
`18 = 3x`

Divide 3 from both sides to isolate x.
`6=x`

Answer 2

`x=6`

Explanation:

Set up a system equation that satisfies the word problem:

`overbrace"When 15 is added"^(15+)` `overbrace"to 7 times a certain number,"^(7x)`

`overbrace"the result is equal to subtracting 3 from 10 times that number."^(=10x-3)`

`15+7x=10x-3`

Move all `x` terms to one side and all non-`x` terms to one side:

`7x-10x=-3-15`

Simplify:

`-3x=-18`

`x=6larr"final answer"`