Answer:
a = -4
Explanation:
Solve for a:
-7 (3 a - 1) = 91
Divide both sides of -7 (3 a - 1) = 91 by -7:
(-7 (3 a - 1))/(-7) = 91/(-7)
(-7)/(-7) = 1:
3 a - 1 = 91/(-7)
The gcd of 91 and -7 is 7, so 91/(-7) = (7×13)/(7 (-1)) = 7/7×13/(-1) = 13/(-1):
3 a - 1 = 13/(-1)
Multiply numerator and denominator of 13/(-1) by -1:
3 a - 1 = -13
Add 1 to both sides:
3 a + (1 - 1) = 1 - 13
1 - 1 = 0:
3 a = 1 - 13
1 - 13 = -12:
3 a = -12
Divide both sides of 3 a = -12 by 3:
(3 a)/3 = (-12)/3
3/3 = 1:
a = (-12)/3
The gcd of -12 and 3 is 3, so (-12)/3 = (3 (-4))/(3×1) = 3/3×-4 = -4:
Answer: a = -4