SOLUTION: In a certain city, the number of commuters decreased 15 percent from June to July and decreased 10 percent from July to August. By approximately what per cent would the number of c

Let x be the desired percent in decimal form.


Then your equation is

    (1-0.15)*(1-0.1)*(1+x) = 1.


It is quite obvious, WHY this equation should be in this form,
so I will not explain it to you for not to be boring :)


Simplify this equation and find x


    0.85*0.9*(1+x) = 1,

    1 + x =  = 1.30719  (rounded).


So, the ANSWER  is  x = 1.30719 - 1 = 0.30719,  or  30.719%.