The force E needed to make a machine pull a load is partly constant and partly varies as the load (L) to be pulled . for a load of 20kg the force needed for a load of 30kg.find (a) the formular connecting E and L (b)E when L=50kg
E = a + bL
Your other information is incomplete, but you can use it to solve for a and b.
Then just find a+50b.