We need first consider what data we have available:
a = run 1.5km
b = then run 2.3km
c = walk 475m
x = a + b + c = how many km he done on treadmill
before we go anywhere, we need to unify the units, we need to change meters to fraction of kilometers, kilo meant 1000, therefore:
1km = 1000m
475m / 1000m = 0.475km
now we can substitute:
x = a + b + c = 1.5km + 2.3km + 0.475km = 4.275km
we can round that up to first decimal point and then:
4.275km = 4.3km
answer is then:
jack done on the treadmill 4.275km or rounded up 4.3km
Let 
be the number of liters of the 10% solution to be used, and 
the number of liters of the 4% solution. The chemist wants to end up with a 4 liter solution, so
For each liter used in the mixture, a concentration of either 10% or 4% acid will be contributed, and the goal is to make a 4L solution whose concentration is 7%, which means
Solving for 
gives 
, so 2L of both solutions is needed.
Answer:
can you please explain that a little more
Those lines stand for the absolute value, or how far away it is from zero.
If you draw a number line from -3 to 3, and plot the points x = 2 and x = -2, what similarities do you see?
Although one is two units to the right of 0 and one is two units to the left of 0, both x = 2 and x = -2 are two units away from zero. Therefore, the absolute value of both 2 and -2 is 2.
The answer to the first part is 3 1/2 and the answer to the second question is 2/7
