Andy had 540 more cards than Henry at first. After receiving 150 cards from Henry, Andy had 4 times as many cards as Henry. How many cards did Henry have at first?
at first:
Hendry had x
Andy had x+540
after the exchange:
Henry had x - 150
Andy had x + 540 + 150 = x + 690
x + 690 = 4(x - 150)
x + 690 = 4x - 600
1290 = 3x
x = 430