Question

How to solve the simultaneous equations 3x + y = 17 and y = x + 1 ?

Answer 1

There are a few ways to do this. In this case the easiest is probably substituting y in the first equation for x+1

so

3x + (x + 1) =17

remove the brackets

3x + x + 1 = 17

combine the x terms

4x + 1 = 17

move the 1 from the LHS to the RHS

4x +1 -1 = 17 - 1

4x = 16

divide both sides by 4

4x/4 = 16/4

x=4

as

y=x+1

y= 4 + 1

y=5