Question

Solve the following system.
y = x + 3
3x + y = 19

A. (7, 4)

B. (−4, 7)

C. (4, 7)

D. (4, −7)

Answer 1

use substitution

Answer 2

y = x + 3
3x + y = 19
--------------
y = ?
so SUBSTITUTE WHAT " y = " in the second equation, like this:
3x + (x + 3) = 19
3x + x + 3 = 19
COMBINE LIKE TERMS (i.e. 3x + x)
3x + 1x + 3 = 19
4x + 3 = 19
SUBTRACT 3 FROM BOTH SIDES:
4x + 3 = 19
-3 -3
---- ----
4x = 16
DIVIDE BOTH SIDES BY 4
4x = 16
-- ---
4 4
x = ?

Answer 3

y= x+3 you can plug the (y) in the other equation to get:
______________________
3x +x+3 = 19
4x+3= 19
4x =19-3
4x = 16
x = 4
________________________
Get (y) by plugging (x) into the equation: (see below)
y = 4+3
y= 7