A student is growing two plants for a science experiment. Each plant was a different height at the start of the experiment. Plant A was given only water and plant B was given water and food. The system of equations show how the heights of the plants, y, in inches have change over x weeks. Plant A: y = 8 + ½ x Plant B: y = 4 + (5/4)x. When did the plants reach the same height?