How do you solve by substitution #a = 3b - 4# and #a + b =16#?

Question

3649 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2018-04-02T14:47:34

#b=5#
#a=11#

#a=3b-4# ----(1)
#a+b=16#----(2)

From (2),
#a=16-b# ----(3)

Sub (3) into (1)
#16-b=3b-4#
#20 = 4b#
#b=5#
#a=11#

Answer 2 · 2018-04-02T14:47:35

#a=11# and #b=5#

We know a in terms of b with the help of equation 1 #a=3b-4#

So put that that in equation 2,
#3b-4+b=16#
Add 4 on both sides
#4b=20#
Divide both sides by 4
#b=5#

Substitute that in one of the original equations

#a+5=16#
Subtract 5 from both sides
#a=11#

So #a=11# and #b=5#