Answer:
a) 4
b) -8
c) 21
Step-by-step explanation:
a) 6a-2b=8
2(3a-b)=8
3a-b=4
b) -2b+6a=8
multiply all through by minus
-(-2b +6a)= -8
2b-6a= -8
c) 6a-2b=8
2(3a-b)=8
divide both sides by 2
3a-b=4
-b =4-3a
multiply both sides by minus
-(-b) = -(4-3a)
b= -4+3a
b=3a-4
a+c=5
c=5-a
13a-4b + c
13a - 4(3a-4) + (5-a)
13a - 12a +16 +5 -a
13a-12a-a+16+5
13a-13a+21
=21