Answer:
C
Step-by-step explanation:
x+4y=-12
x+7y=-15
subtract
-3y=3
y=-1
x+4(-1)=-12
x=-12+4=-8
so point is (-8,-1)
A + b = 15 ..... eq 1
a – b = 12 ...... eq 2
So a = 15 – b
Substitute in eq 2 :
15 – b – b = 12
15 – 2b = 12
–2b = 12 – 15
b = 1.5
So a = 15 – 3/2 = 13.5
4ab = 4 x 13.5 x 1.5 = 81
100,000
because the 8 makes the 9 round up into a 10
I'll assume the above equation is: 9 - 7x = 7 - 4(2x+3)
* do distributive multiplication
9 - 7x = 7 - 8x - 12
*move like terms
-7x + 8x = 7 - 12 - 9
* solve for x
x = 7 - 21
x = -14
To check, substitute x by its value -14
9 - 7x = 7 - 4(2x+3)
9 - 7(-14) = 7 -4[2(-14) + 3]
9 + 98 = 7 - 4(-28 +3)
107 = 7 - 4(-25)
107 = 7 + 100
107 = 107