Let's translate each sentence into "Math".
Pineapple = p
Orange = x
is means equal
Pineapple is 7 times as heavy as an orange: p = 7x
Pineapple weighs 870 grams more than orange. p = 870 + x
Substitute p = 7x into the second equation:
7x = 870 + x
Subtract x from both sides
6x = 870
divide by 6
x = 145
The orange weighs 145 grams.
The pineapple weights 7 times the orange = 7(145) = 1015 grams.
