Inverse function: 
y=2x+5 use are suppose to change the "y position" into x position.
x=2y+5 then it's already changed, so Y is required to find its value?
2y=x-5 transposition of constant no.5
2y/2=x-5 to find your Y isolate it by dividing both side by 2 to remove our constant.
y=x-5/2 This the final answer or the value of y in a given question.
1 5 1