Answer:
a) 9x + 7y = 279
3x + 5y = 135
b) X (Weight of each large box) = 18.75 kilograms
Y (Weight of each small box) = 15.75 kilograms
Explanation:
Let's assume:
X is weight of each large box
Y is weight of each small box
First, multiply the opposite number to get the same value of y:
9x + 7y = 279 ..... ×5
3x + 5y = 135 ...... ×7
Second, here comes the outcome of the multiplication from both side:
45x + 35y = 1,395
21x + 35y = 945
24x = 450
x = 18.75 kg
if x = 18.75, then:
3x + 5y = 135
3×(18.75) + 5y = 135
56.25 + 5y = 135
5y = 135 - 56.25
5y = 78.75
y = 15.75 kg
If you try to input the x and y value into the part a) equation, then you will get the same total weight for first and second delivery respectively.
Hope it helps. Thanks!