Explanation:
the slope-intercept form is
y = ax + b
"a" being the slope, "b" being the y-intercept (the y-value when x = 0).
we see that with every increase of x by 1 y increases by 3.
so, the slope "a" is 3.
to get b we use one of the given points, e.g. (1, 5) :
5 = 3×1 + b = 3 + b
b = 2
so, our function is
y = 3x + 2