Let's convert each statement into mathematical terms.
Pineapple = p
Orange = x
is indicates equality
Pineapple has a weight that is 7 times that of an orange: p = 7x
Pineapple is 870 grams heavier than the orange. p = 870 + x
Insert p = 7x into the second equation:
7x = 870 + x
Subtract x from both sides
6x = 870
Divide by 6
x = 145
The weight of the orange is 145 grams.
The weight of the pineapple is 7 times that of the orange = 7(145) = 1015 grams.
The solution to the query
Gabe mowed 5 lawns and made $150.
