(x + 1) + (x + 2) + (x + 3) + ... + (x + 26) = 377
=> x + 1 + x + 2 + x + 3 + ... + x + 26 = 377
=> (x + x + x+ ... + x) + (1 + 2 + 3 + ... + 26) = 377
=> 26x + \(\frac{\left(26+1\right).26}{2}\)=377
=> 26x + 351 = 377
=> 26x = 377 - 351
=> 26x = 26
=> x = 1
< = > 26x + 26.27:2 = 377
26x + 351 = 377
26x = 377 - 351 = 26
x = 26 : 26 = 1