How do you solve the system x = 5 - yx=5y and 3y = 3x + 13y=3x+1 by substitution?

1 Answer
May 28, 2015

We can substitute the xx of the first equation into the second:

->3y=3*(5-y)+13y=3(5y)+1
->3y=15-3y+13y=153y+1
->6y=16->y=16/6=8/36y=16y=166=83

Now plug that into the first equation:
x=5-8/3 =15/3-8/3=7/3x=583=15383=73

So x=7/3 and y=8/3x=73andy=83

Check your answer with the second equation:

3* 8/3 = 3* 7/3 +1 ?-> 8=7+1383=373+1?8=7+1 Check!