Question 883587
The problem says that 78 is 20% more than what Nina saved in Feb. 

Since we do not know what is the quantity she saved in Feb let's call that x.

So, turning this into an equation we have...

78 = x + x(.20)

Why x + x(.20)? Because the problem is basically telling us that the sum of what she saved in Feb (x) and 20% of x will result in 78. To find 20% of x we multiply x(.20)

Now...

78 = x + .20x

Let's multiply both sides by 100 to get rid of that nasty decimal.

7800 = 100x + 20x

7800 = 120x

Now it's just a matter of isolating x. We divide each side by 120 which gives us...

x = 7800/120 

x = 65

Verify now...

65 (what she saved in Feb) plus 20% percent of that should give you 78.

65 + 65(.20)

= 65 + 13 

=78

Voila!