If you triple me, subract 7, and add 4 you get 42. What number am i?

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If you triple me, subract 7, and add 4 you get 42. What number am i?

Start with an unknown number, "x".

Triple me
3x

Subtract 7
3x - 7

Add 4
3x - 7 + 4

You get 42
3x - 7 + 4 = 42

Simplify:
3x - 3 = 42

Run this through our equation calculator:
x = 15