(15 PTS answer asap pls) Can someone explain how I got this wrong? I´m too scared to ask my teacher because we´ve moved on already

In your original answer, you did not distribute the 7 to the 3j

Step-by-step explanation:

The distributive property basically states that the sum of any variables multiplied by a factor is equal to the sum of each product of every individual variable and the factor.

In short,

a(b+c) = ab + ac

or

x(y + w + z) = xy + xw + xz

or

9m + 9n = 9 (m+n)

Therefore, in order to solve 7(3j + 10)

you must multiply 7 by 3j and 7 by 10

(7 * 3j) + (7 * 10) = 21j + 70

Since 70 does not have the same terms as 21j (70 does not have j),

21j + 70 is in its most simplified form.

In your original answer, you didn't multiply the 3j by 7.