I just need help seeing part of how this is solved. These are my notes from class. The parts I do not understand are in red.

u=2x-5

du=2dx

1/2du=dx

2x=u+5

2u+10=4x

2u+13=4x+3

I do not understand how we we concluded that if 2x=u+5 that 2u+10=4x and 2u+13 = 4x+3.