How do we remove the extra variable from one side?? e. g
2n = n - 1

how do we remove the variable next to the -1

By transposing the variable from RHS to LHS

2n=n-1

2n-n=-1

n=-1

x is the total time in minutes for the free response

you are given number of questions as 15 - m and time per item as 8 minutes

to find x multiply the two givens together:

x = 8 * (15-m) = 8(15-m)