What is five ninths plus four sixths

Pls! does anybody know a shortcut for answering these types of questions in the future?

Which value would be a solution for x in the inequality 47-4x< 7

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 (%)