Let us suppose the number of balloons purchased is x in number.
It is given balloons are purchased for $.79 each
Cost of x balloons = .79x.
Total amount spent on purchasing balloons = $11.85
Cost of x balloons = Total cost of balloons.
.79x=11.85
With x .79 is multiplied .Opposite of multiplication is division.
We perform the opposite operation both sides
Dividing both sides by .79
x=11.85÷.79
x=15
Total number of balloons purchased is 15.