Since m + n = 7 we know m = 7-n. So now we have 2n - 3(7-n) = 6. From this we get n = -3. So now we know m - 3 = 7 so m = 10. So now we have 3(-3) + 2(10) = ? and this comes out as 11
In the step after -6x+10=4x+20, he moved the terms incorrectly. you have to add 6x to both sides so it would be 10=4x+6x+20 which simplifies to 10=10x+20. subtract 20 from both sides to get -10=10x. divide both sides by 10. the answer is x=-1

Plug in what we know:

Find the cube root of both sides:
![\sf~a=\sqrt[3]{2744}](https://tex.z-dn.net/?f=%5Csf~a%3D%5Csqrt%5B3%5D%7B2744%7D)
Simplify:
Answer:
7
Step-by-step explanation:
Sub -1 in for each x:
-3x³-4x
-3(-1)³-4(-1)
-3(-1)+4
3+4
7