Question

78 + (−65) + ---------------
= 80

Answer 1

Answer:

The answer is 67.

Step-by-step explanation:

Let the unknown number be x.

78+(-65)+ x= 80

78-65+x= 80

13+x=80

x=80-13

x= 67

Answer 2

Given:

The mathematical equation - 78 + (−65) + ------- = 80

To Find:

The missing number

Solution:

Let the unknown number be = x.

Substituting the value in the equation -  

Thus,

78+ (-65) + x =  80

78 - 65 + x = 80

13 + x =80

x = 80-13

x = 67

Therefore, the missing number is 67

Checking: The correct placement will be  -

78 + (−65) + 67

= 145 - 65

= 80

Answer: The correct mathematical equation is - 78 + (−65) + 67 = 80