3 apples and a pineapple equally balances 10 oranges. Also,6 oranges and an apple equally balances a pineapple. How many oranges balance a pineapple?

Answer 1

3 a + p = 10 o

6 o + a = p write as 3 a + 18 o = 3 p

so now
3 a + p = 10 o
3 a + 18 o = 3 p
------------------subtract
p - 18 o = 10 o - 3 p

4 p = 8 0
1 p = 2 o
so
two oranges balance a pineapple