Math help

Well....by the use of the word "increase" or "decrease" in the questions themselves, we should be able to  answer the first  part

Here's 1

Note something important   we can write an  "x"  percent increase  as

(1  +  the decimal representation of the percent increase )

So......this becomes

84  ( 1 + 12%)  =  84 ( 1 + .12)  =  84 ( 1.12)  =  94.08

Here's 2

Likewise.....we can write an "x" percent decrease  as

(1 -  the decimal representation of that decrease )

So we have

820 ( 1 - 25% )  =  820 ( 1 - .25)  =  820 (.75)  = 615