a, 52x - 3 - 2.52 = 52.3
=> 52x - 3 - 50 = 75
=> 52x - 3 = 125
=> 52x - 3 = 53
=> 2x - 3 = 3
=> 2x = 0
=> x = 0
vậy_
b, (x + 1) + (x + 2) + ....+ (x + 100) = 5750
=> x + 1 + x + 2 + ... + x + 100 = 5750
=> (x + x + x + ... + x) + (1 + 2 + 3 + ... + 100) = 5750
=> 100x + 5050 = 5750
=> 100x = 700
=> x = 7
vậy_