distributive property of multiplication states: a(b+c) is equal to (ab + ac).
So in your case we need two numbers inside the parentheses that add up to 26. Pick any combination.
let's try 14 and 12.
so we have:
3(26) = 3(14 + 12) = (3* 14 + 3 * 12)
3(26) = 78
(3* 14 + 3 * 12) = (42 + 36) = 78
therefore, a(b + c) = (ab + ac)