For every input value, that is x, there is a corresponding output value that is y. Therefore;
[tex]\begin{gathered} m=\frac{y_2-y_1}{x_2-x_1} \\ m=\frac{10-4}{-2-\lbrack-4\rbrack} \\ m=\frac{6}{-2+4} \\ m=\frac{6}{2} \\ m=3 \\ \text{Therefore;} \\ y=mx+b \\ We\text{ can use any of the given points. We shall use the first point given (-4,4)} \\ 4=3(-4)+b \\ 4=-12+b \\ 4+12=b \\ b=16 \\ \text{With the values of m and b now derived;} \\ y=mx+b \\ y=3x+16 \end{gathered}[/tex]
The equation is y = 3x + 16
Therefore when the input (x value) is 20, the output is given as;
y = 3(20) + 16
y = 60 + 16
y = 76
