35=14x-0.7x^2

Solution for 35=14x-0.7x^2 equation:

35=14x-0.7x^2

We move all terms to the left:

35-(14x-0.7x^2)=0

We get rid of parentheses

0.7x^2-14x+35=0

a = 0.7; b = -14; c = +35;
Δ = b2-4ac
Δ = -142-4·0.7·35
Δ = 98
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{98}=\sqrt{49*2}=\sqrt{49}*\sqrt{2}=7\sqrt{2}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-14)-7\sqrt{2}}{2*0.7}=\frac{14-7\sqrt{2}}{1.4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-14)+7\sqrt{2}}{2*0.7}=\frac{14+7\sqrt{2}}{1.4}
$