Question 31376
x = Sylvia.  Then Lori(L) = x+50, and Diane(D) = L+40, and Shannon(S) = D+70. 
You are on the right Path
Diane = L+40
but we know that L = X+50
So D = X+50+40 = X+90
Similarly Shannon = X+90+70 = X+160

So total earnings = X + X+50 + X+90 + X+160 = 4X +300
But total we know is $1,500
So 4X+300 = 1500
Subtracting 300 on both sides
4X = 1200
X = 1200/4
X = 300

I hope you can find the rest of the earnings from here :-)