Hi,
a line is define by the following equation : y = ax+b
where a is the slope, and b the value for x = 0
so you have : a*3 +b = 3 for the first point
a*(-5) +b = 4 for second point
so you have a system : 3a+b =3
-5a+b = 4
so : 3a+b -(-5a) -b = 3-4
3a+5a +b-b = -1
8a = -1
a = -1/8
then a = -1/8 so , in remplacing a by it's value in one equation , b is : 3(-1/8) +b = 3
-3/8 +b = 3
b = 3 +3/8
b = 24/8 +3/8
b = 27/8
let's check : 3 (-1/8) + 27/8 = -3/8 +27/8 = 24/8 = 3
first point is correct
-5( -1/8) + 27/8 = 5/8 +27/8 = 32/8 = 4
second point is correct
line is y = -1/8X +27/8
