Answer:
Step-by-step explanation:
7) a - 4b -c = -20 -------------(I)
3c = -6 ------------------(II)
2a +5c = -22 ---------------(III)
3c = -6 {Divide both sides by 3}
c = -6/3
c = -2
Plugin c = -2 in equation (III)
2a + 5c = -22
2a + 5*(-2) = -22
2a - 10 = -22
2a = -22 + 10
2a = -12
a = -12/2
a = -6
Plugin a = -6 and c = -2 in equation (I)
a - 4b -c = -20
-6 - 4b -(-2) = -20
-6 - 4b + 2 = -20
-4b - 4 = -20
-4b = -20 + 4
-4b = -16
b = -16/4
b= -4
8) b = 2a - 9 -----------(I)
3a - 3c = 21 -------------(II)
c = a -5b- 22
-a + 5b + c = -22 -----------(III)
Multiply equation (III) by 3 and then add to equation(II)
(III)*3 -3a + 15b + 3c = -66
(II) 3a + 0b - 3c = 21 {Now add}
15b = -45 {Divide both sides by 15}
b = -45/15
b = -3
Plugin b = -3 in equation (I)
b = 2a - 9
-3 = 2a - 9 {Add 9 to both sides}
-3 +9 = 2a
2a = 6 {Divide both sides by 2}
a = 6/2
a = 3
Plugin a = 3 in equation(II)
3a - 3c = 21
3*3 - 3c = 21
9 - 3c = 21 {subtract 9 from both sides}
-3c = 21 - 9
-3c = 12 {Divide both sides by 2}
c = 12/-3
c = -4
