Math math math help asap

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.

Having a hard time understanding this question (see attachment).

Which number line correctly shows 0.8 + 0.3?