60=-7t+4.9t^2

Solution for 60=-7t+4.9t^2 equation:

60=-7t+4.9t^2

We move all terms to the left:

60-(-7t+4.9t^2)=0

We get rid of parentheses

-4.9t^2+7t+60=0

a = -4.9; b = 7; c = +60;
Δ = b2-4ac
Δ = 72-4·(-4.9)·60
Δ = 1225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1225}=35$
$t_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7)-35}{2*-4.9}=\frac{-42}{-9.8}
=4+2.8/9.8
$
$t_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+35}{2*-4.9}=\frac{28}{-9.8}
=-2+6/7
$