3a-b=13 and b=2a -7 in substitution method

Question

in substitution method need to find what a equals and what b equals need these answers ASAP thanks so much.

Answer 1

3a-b=13 ... first equation

 

3a - (2a -7) = 13 ...OBSERVE THAT within parentheses I have SUBSTITUTED for b, using the second equation.

 

Now I have one equation and just one unknown.  You and I can solve that, getting a = 6. Then put that into the second equation and you will have b.