10 = -2c + 22, turns into -12 = -2c because we must move the 22 over to the left side, and since it is positive, we must do the opposite operation
-12 = -2c, then turns into 6 = c, because we need to get the c by itself. To do so we divide both sides by -2, and when two negative numbers are divided together, the resulting number is positive
you just add the number of songs that she already knows how to play plus the number of songs that she learns to play the next week then you have your answer
