104
Step-by-step explanation:
Let x = the unknown second number. 2/5 of [the sum of] two numbers is 56. One of the numbers is 36:
(2/5)(36+x) = 56
Multiply both sides by 5/2:
36 + x = 56*5/2
36 + x = 140
x = 104
Check:
(2/5)(36+104)=56
(2/5)(140)=556
280/5 = 56
56 = 56
Check!