You would start out with the equation (y2-y1) over (x2-x1). So to solve this problem it would be (12-(-10) over (4-1) and your answer would be 22/3.
Basically (g of f)x=(f(g(x)) so
g of f=f(g(x))=7(5x^2+4x-3)+5
distribute
f(g(x))=35x^2+28x-21+5=35x^2+28x-16
g of f=35x^2+28x-16
Let x be the unknown number and let's set up an equation.
12x - x = 143
Now solve for x:
11x = 143
x = 13
The positive number is 13.
