a) 754⋅78 + 3.900:65-276⋅53

1) $$754 \cdot 78 = 58812$$

   754
 x 78
------
  6032
+5278
------
58812

2) $$3900 : 65 = 60$$

   60
65|3900
   390
  -----
    00
    0

3) $$276 \cdot 53 = 14628$$

  276
x 53
----
  828
+1380
-----
14628

4) $$58812 + 60 - 14628 = 44244$$

 58812
+   60
------
 58872
-14628
------
 44244

Ответ: 44244