Answer:
b = -3
Explanation:
Solve for b: 
4 b - 4 2 + 24 = 20 - 16 
 
-4×2 = -8: 
4 b + -8 + 24 = 20 - 16 
 
Grouping like terms, 4 b - 8 + 24 = 4 b + (24 - 8): 
4 b + (24 - 8) = 20 - 16 
 
24 - 8 = 16: 
4 b + 16 = 20 - 16 
 
20 - 16 = 4: 
4 b + 16 = 4 
 
Subtract 16 from both sides: 
4 b + (16 - 16) = 4 - 16 
 
16 - 16 = 0: 
4 b = 4 - 16 
 
4 - 16 = -12: 
4 b = -12 
 
Divide both sides of 4 b = -12 by 4: 
(4 b)/4 = (-12)/4 
 
4/4 = 1: 
b = (-12)/4 
 
The gcd of -12 and 4 is 4, so (-12)/4 = (4 (-3))/(4×1) = 4/4×-3 = -3: 
Answer: b = -3