About 42% of a paint mix is white. a painter orders 18 gallons of the paint mix. how much of it is white.

If you have the percentage of an amount, you just have to multiply the amount by the decimal form of the percentage.  The decimal form of a percentage is the percentage divided by the 100 (or, moving the decimal place two spaces to the left).

In this case, the percentage is 42%, so we multiply 18 by 0.42 to get the

18 gallons × 0.42 = 7.56 gallons

7.56 gallons of it is white.

Ithink it's the first one ( let me know if it right)