How do you get rid of 1/3? 1/3+a = 6/3

Acompany that manufactures and sells guitars made changes in their product range. from the start they had 20 models. then they reduced the number of models to 15. as a result, the company enjoyed a 10% increase in turnover. - how much did the stock level change? in (%)

With number 11 ( show how you got the answer)

Two numbers have a sum of -19. one number is x. what expression represents the other number?