y = mx + b
slope(m) = 3/4
(3,7)...x = 3 and y = 7
now we sub...we r looking for b, the y int
7 = 3/4(3) + b
7 = 9/4 + b
7 - 9/4 = b
28/4 - 9/4 = b
19/4 = b
equation is : y = 3/4x + 19/4...lets put this in standard form
y = 3/4x + 19/4
-3/4x + y = 19/4...multiply by -4
3x - 4y = -19 <== standard form
if (x,5) is on the line
3x - 4y = -19.....sub in 5 for y
3x - 4(5) = -19
3x - 20 = -19
3x = -19 + 20
3x = 1
x = 1/3 <====so point a = (1/3,5)
