the volume of cuboid is given by length*breadth*height
the volume of above cuboid is 6*12*125=864cubic in.
volume of below cuboid is 18*10*8=1440 cubic in.
totoal volume = 1440+864l=2304 cubic in.
Convert the fractions so they both have the same denominator (bottom part of the fraction)
1/5 = 7/35
This is because 5*7=35, so 1*7=7
1/7 = 5/35
This is because 7*5=35, so 1*5 =5
Then subtract the top numbers to get the answer:
The answer should be 3 :)
You literally need to apply the formula

where
is the mass and
is the speed