Help me pls I will mark you as questions 5 pls

Agrocery store has 12 lb of trail mix that is 10% banana chips. the store's manager would like to add banana chips to bring the new mix up to 25% banana chips. write and solve a system of equations to find out how many pounds of banana chips manager needs to add.

With this question! what is process of elimination? ? p.s. my brothers acc got banned so add his new one @ yamauchiyamyam17

45% of the trees in a park are apple trees. there are 27 apple trees in the park. how many trees are in the park in all?