The student wrote the wrong operation. "The sum of 5y and 3" translates to 5y+3. And here means addition.
Your anwser is quit school ):73
Let's say that the value invested in the account with a rate of 8% is "x", then the amount invested in the account with a rate of 12% is:

To calculate the total interest we need to calculate the interest of each individual account and sum them:

The total interest is the sum of the two expressions above:

The value invested in the account with 8% interest is 830, the one invested in the account with 12% interest is 1280.
Answer:
I think the answer are C, B, C, and A.
GCF is 5m^2 n^2
m^2 has exponent 2 and n^2 has exponent 2
(1) m^5n^5
here there is no 5 so it does not have GCF
(2) 5m^4n^3
m^4 has exponent 4 greater than exponent 2
n^3 has exponent 4 greater than exponent 2
5m^4n^3 have GCF
(3) 10m^4n
10 is 5*2 . it has GCF 5
m^4 has exponent 4 greater than exponent 2
n has exponent 1 less than exponent 2
10m^4n does not have GCF
(4) 15m^2n^2
15 is 3*5 which has GCF 5
m^2 has exponent 2 which is equal to exponent 2
n^2 has exponent 2 which is equal to exponent 2
15m^2n^2 have GCF
(5) 24m^3n^4
24 is 2*2*2*3 does not have GCF
m^3 has exponent 3 greater than exponent 2
n^4 has exponent 4 greater than exponent 4
24m^3n^4 does not have GCF