So you have to multiply the 2 and the n first and the 2 and the 5.
So that's 2n+10. Next, you have to subtract 10 from both sides and cross the previous 10 out (because they cancel out). Then, you bring down the 2n and the -12.
(2n-12) Last you divide everything by 2 and you get:
n=-6!
TA-DA!!!