Answer: 28
Explanation:
Let the number of balloons that she had last party be represented by x.
Since Mrs.Hines has 40 ballons for a party which was 12 more balloons than she had for her last party. The number of ballons had last party will be formed into an equation as:
x + 12 = 40
Collect like terms
x = 40 - 12
x = 28
She had 28 balloons last year