The first 3 common multiples of 5 and 15 are 15, 30, and 45. Remember that the number itself is also a multiple of any number, since you can multiply it by 1.
2
x
+
3
y
=
12 is the standard form for a linear equation. To determine the slope, solve the equation for y in order to convert to the slope-intercept form y
=
m
x
+
b
, where m is the slope and b is the y-intercept.