Answer:
Last year, a small business had a total revenue of $a
This year, this business had a total revenue of $55,200
If this year's total revenue is 15% more than last year's total revenue, the equation expressed the relation between these 2 years' revenue is:
a + 15% of a = 55200
<=> a + (15/100)a = 55200
<=> a x (115/100) = 55200
=> a = 55200 x 100/115 = 48000
=> Last year's revenue: a = 48000$
Hope this helps!
:)