this is your answer, i hope this helps you
The answer is: "72" .
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(input value, or "x") / 10 = y = f(x);
When y = 7.2, what is the value of "x" ?
x / 10 = 7.2 ;
x = (7.2) * 10 = 72 .
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y=23x+143 hope this helps