for both questions u need to remember the general formula for inverse proportion which is x=k/y. k stands for constant. for a, u need to find what is the k first then u will be about to solve the question. the formula i wrote is t=k/w is because t which is time is inversely proportion to the numbers of workers, w that is why i wrote that. for b u need to find the first force applied and the second force applied. the second force applied u need to have a 20% increase. afterwards u just find the percentage reduced