y = mx + b is the slope intercept formula
to find m (slope), with 2 points given, use the formula y2-y1/x2-x1
So, 10-0/2-0 = 10/2 = 5.
The slope is 5, so if u replace it in the equation that would give you y = 5x + b.
b is the y- intercept, and y intercept here is 0. how? well, y intercept is a point where x is 0, so for example. If u have a point (0,3) the y intercept would be 3, BUT in this question its (0,0) so, the y intercept is 0 which you don't have write in the equation.
So the answer is y = 5x