Sum \ (multiple+1) = decimal.

Decimal × multiple = large number

(or sum-decimal = large number)

Difference problem

Difference ÷ (multiple-1) = decimal

Decimal × multiple = large number

(or decimal+difference = large number)

Pear tree: 120(4- 1)= 40 (tree)

Apple tree: 40×4= 160 (tree)