Simplify (3m+10a-15)+(5a+20)

$(3 m + 10 a - 15) + (5 a + 20)$

Remove parentheses.

$3 m + 10 a - 15 + 5 a + 20$

Add $10 a$ and $5 a$ .

$3 m + 15 a - 15 + 20$

Simplify the expression.

Add $- 15$ and $20$ .

$3 m + 15 a + 5$

Reorder $3 m$ and $15 a$ .

$15 a + 3 m + 5$