if greg buys 3 shirts , 6 trousers and 4 ties , the total cost is $ 80 . if greg buys 7 shirts , 2 trousers and 4 ties , the total cost is $ 80 . how much will it cost him to buy 5 trousers , 4 shirts and 4 ties ?
"solution : 3 x + 6 y + 4 z = 80 7 x + 2 y + 4 z = 80 adding both the equations = 10 x + 8 y + 8 z = 160 5 x + 4 y + 4 z = 80 ans c"
divide(add(80, 80), 4)