so its 20 fixed or constant. so that +20
the 30 varies absed on teh number of days which is unknown . so that's 30x
do f(x)= 30x + 20
so for 4 days its
f(x) = 30(4) + 20
f(x) = 120+ 20 = 140
We let the amount of 32% acid solution added to be X ,
Firstly, 40 of 0.12 conc. , = 4.8L of acid, and 35.2L non acid
For ever 1 L of 32% acid we add in we get 0.32L of acid and + 0.68L non Acid,
So we formulate an equation
(4.8+0.32X) / (40+X) = 16/100
(4.8+0.32X) = 0.16(40+X) =6.4+0.16X
0.16X = 1.6
X =10
Hence she used 10L of 32% Solution acid.
If the train travels 18 mph you just have to divide 270 by 18 and that would be your answer.
So 270/18 = 15 which means it would take the train 15 hours to travel 270 miles.
F x (x + h) - fx/h
fx +fh - fx /h
fh/h
f
So f is the answer