First lets write down our starting conditions:
we have 22 gallons and it has 16% of ammonia
16% of 22 gallons is
A = 16/100*22 = 3,52 gallons
Now since only watter is evaporating that means that in second scenario after some watter evaporated there is still 3,52 gallons of ammonia. But now those 3,52 gallons of ammonia represent 24% of total mixture. So now we go other way.
24 % is 3,52 gallons
100% is x gallons
x = 100/24*3,52 = 14.667 gallons
That means that he has to evaporate
22 - 14.6667 = 7,333 gallons of water.
a. We're looking for 
such that
b. Integrating with respect to 
will make things easier.
(where we take the positive square root because we know 
)
Now we want to find 
such that
The correct answer is d15
It’s a. Start at the y intercept and rise over run to the next point.
Yesterday Hadi earned: $120
Today he will earn: $120*85% = $102
(You times the amount yesterday by 85% because you want to find the 15% less of 100% of the amount he's earned yesterday. Therefore, to find 15% less than yesterday you multiply it by 85% (100% - 15%) )
Tomorrow he will earn: $102*115% = $117.30
(Same thing here, however you are finding 15% more than 100% today. Therefore, you multiply the amount he earned today it by 115% (100% + 15%) )
To find the amount he earns for the three days you must add the amount earned of yesterday, today and tomorrow earned from the working above.
Therefore, Hadi expects to earn:
Yesterday + Today + Tomorrow = 120 + 102 + 117.30 = $339.3
