HELP !!!

collect like terms 10u+5v-6u-7v -5v -5v=-2 -10u -10u =-16 answer=-18 is my answer correct

During multiplication by 10,100,etc, why is it that the digits move one or more places to the left depending on the number of zeros?what's the logic? Ex: 24X10=240, 24X100=2400.

During decimal multiplication, we know that the placement of the decimal point in the product is decided by the sum of number of digits after the decimal point in both the factors being multiplied. I know that's what we do but i don't understand why this...

Why hexagons are the most extensively found shapes in nature?what is the mathematical reason?What makes them so efficient? Why heptagon,octagon etc are not preffered over hexagon?