How do I solve using substitution

Question

2x-15y=35

-x+5y=-16

Answer 1

Isolate a variable in one of the equations and then plug into the other.

 

-x = -16 -5y

x = 16 +5y

 

Now plug in.

 

2(16+5y) - 15y = 35

32 + 10y -15y = 35

-5y = 3

y = -3/5

 

x = 16 + 5(-3/5)

x = 16-3

x = 13

 

You can then check your work.

 

-(13) + 5(-3/5) = -16

-13 - 3 = -16

-16 = -16

 

2(13) - 15(-3/5) = 35

26 + 9 = 35

35 = 35