The average white rhinoceros gives birth to a single calf that weighs about 3.8% as much as its mother. if the mother rhinoceros weighs 3.75 tons, about how many pounds does its calf weigh? 

There are 2000 pounds in a ton - so the rino weighs 3.75 x 2000 = 7500 pounds

a percentage can be converted to a decimal - if you want to know what 3.8% of a number is, move the decimal two spaces to the left 3.8% is 0.038 - 

Multiply 7500 pounds by 0.038 - the answer is 285 pounds.

Element 17 is chlorine it is a group 7 element(halogen) and belongs to period 3 of the periodic table