I'm not sure exactly what you're asking but 1×10^-5 is .00001. I could be interpreting your question wrong in which case I'm sorry.
Part(A):
To solve the system of Linear equations using Substitution:

Consider the first equation, x+y=7 implies x=7-y













PArt(B): Use a graph to verify your answer to the system:
Using Desmos graphing calculator, graph the two equations.
Y intercept is -7
Look at the picture to see what I did