Step-by-step explanation: To find the values of l and m, we need to solve the equation 15 - 28i = 3l + (4m)i for l and m.
First, we can move all the terms with i to one side of the equation:
15 = 3l + 4mi
-28i = 4mi
To solve for m, we can divide both sides by 4i:
-28i/4i = m
m = -7
Now that we know the value of m, we can substitute it back into the equation to solve for l:
15 = 3l + 4(-7)i
15 = 3l - 28i
3l = 15 + 28i
To solve for l, we can divide both sides by 3:
l = (15 + 28i)/3
So the values of l and m are l = (15 + 28i)/3 and m = -7