If f(0) = -2 that means, when you put zero instead of x in the f(x) equation, it gives -2 as answer. m is given as 2/3. So,
f(x) = mx + b
f(0) = 2/3 * 0 + b = -2 then b = -2
Then you can write the general function as ;
f(x) = 2/3*m -2
And same steps for question 25;
m is given as -1/3
f(9) = -1/3 * 9 + b = 2 then b must be 5
Then the general form of the function;
f(x) = -1/3*m +5
