If I understand your question right, this is not necessary, but is very useful to keep problems organized.
Given :
A submarine started at the surface of the water and was moving at -15 meters per minute.
The submarine traveled at this rate for 48 minutes before coming to rest on the ocean floor.
To Find :
The change in the submarine position.
Solution :
We need to find the position of submarine position from the surface of water.
Distance travelled = Speed × Time
Distance travelled = -15 m/min × 48 min
Distance travelled = 720 m
Therefore, the position of submarine is 720 m below the surface of ocean.
<span>Cross multiply:
2 * n = 5 * 12
Simplifying
2 * n = 5 * 12
Multiply 5 * 12
2n = 60
Solving
2n = 60
Solving for variable 'n'.
Move all terms containing n to the left, all other terms to the right.
Divide each side by '2'.
n = 30
Simplifying
n = 30</span>
(-1/2) and (-3/4)... multiply numerators and denominators and you will get 3/8