Question

108 - 271 + 215-_____= -103

Answer 1

108-271+215-_____=-103
Im going to combine the first thee numbers and replace the blank with a variable, lets use x. 
52 - x=-103
now I am going to subtract 52 on both sides to get the variable alone
-x=-155
Im going to multiply both sides to eliminate the negitive in the variable
x=155
If you want to check just plug 155 into the blank
108-271+215-155=-103
-163+215-155=-103
52-155=-103
-103=-103

so after checking work the blank is equal to 155.