For 31 you need 6% OF 50 meaning you need to multiply. 50*0.06=3. The answer for 31 is 3.
To find 33 you need to divide 1 by 0.4 to find how much you need to multiply 28 by. 1/0.4= 2.5 then you need to do 2.5*28 which would equal 70. The answer for 33 is 70.
To find 35 you need to notice that it DECREASES in meaning the bigger number (20) would be the denominator of the fraction and 15 would be the numerator. Therefore the fraction would b 15/20 or 75% of 20 would equal out to 15.
So to set up the equation we have:
<span><span><span>4M</span><span>4+M</span></span>=<span>127</span></span>
<span>28M=12(4+M)</span>
<span>28M=48+12M</span> <span>28K−12M=48</span>
<span>(28−12)M=48</span>
<span>16K=48</span>
<span>M=<span>4816</span></span>
<span>M=3</span>
So Marna can clean the chimney alone in 3 hours
