Find the equation of the line and plug in the x value that gives you which is -3? i am not very sure so i am sorry if i am wrong
This is an example hope this helps
\left[x \right] = \left[ 0\right][x]=[0]
We first add both 19.8 by 19.8 and therefore, that would give us 39.6.
42 - 39.6 = 2.4.
2.4 ÷ 2 = 1.2
1.2 would be the length of each sides.
X=4
cross multiply
3x=12
x=4