Answer: Choice A
7(10+9) = 70 + 63
============================
Explanation:
when we multiply 7 by 19, we start off multiplying just 7*9 = 63 so just focus on the units or ones digit of 19 to have it multiply with 7. We have 63 as the result so we write down "3" as part of the answer, and carry the 6.
Then you move onto the tens digit. The tens digit of 19 is 1. Multiply 1 by 7 and we get 7, which adds on to the carry digit 6 to get 7+6 = 13. Therefore we'll stick a 13 in front of the 3 we got earlier to end up with the final answer 133
---------------
Using the distribution rule is much easier in my opinion
19 = 10+9
7*19 = 7*(10+9)
7*19 = 70+63
7*19 = 133
The idea is to multiply the outer 7 by each term inside the parenthesis
7*(10+9) = 7*10 + 7*9 = 70 + 63
So we multiplied the 7 by the 10 first to get 7*10 = 70
Then did the same for the 9 term as well 7*9 = 63
After those two multiplications, we add the results up: 70+63 = 133
