X(7+x)=60

Solution for X(7+x)=60 equation:

X(7+X)=60

We move all terms to the left:

X(7+X)-(60)=0

We add all the numbers together, and all the variables

X(X+7)-60=0

We multiply parentheses

X^2+7X-60=0

a = 1; b = 7; c = -60;
Δ = b2-4ac
Δ = 72-4·1·(-60)
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$X_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7)-17}{2*1}=\frac{-24}{2}
=-12
$
$X_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+17}{2*1}=\frac{10}{2}
=5
$