I’m in ninth grade and don’t understand this algebra 1 question -5(3a+b)+(2a-7b)

-13 a - 12 b

Step-by-step explanation:

Simplify the following:

-5 (b + 3 a) + 2 a - 7 b

Hint: | Distribute -5 over b + 3 a.

-5 (b + 3 a) = -5 b - 15 a:

-5 b - 15 a + 2 a - 7 b

Hint: | Group like terms in -5 b - 7 b + 2 a - 15 a.

Grouping like terms, -5 b - 7 b + 2 a - 15 a = (-5 b - 7 b) + (-15 a + 2 a):

(-5 b - 7 b) + (-15 a + 2 a)

Hint: | Combine like terms in -5 b - 7 b.

-5 b - 7 b = -12 b:

-12 b + (2 a - 15 a)

Hint: | Combine like terms in 2 a - 15 a.

2 a - 15 a = -13 a:

 -13 a - 12 b