Answer:
65.
Step-by-step explanation:
Let x represent our required number.
We are asked to find the number which is equal to 78 when increased by 20 percent.
After increasing by 20%, our number would be [tex]x+\frac{20}{100}x=x+0.20x=1.20x[/tex].
To solve for x, we will set an equation as:
[tex]1.20x=78[/tex]
[tex]\frac{1.20x}{1.20}=\frac{78}{1.20}[/tex]
[tex]x=65[/tex]
Therefore, our required number is 65.