Simplify each sum :

1/2x + 1/2x

Element x decays radioactively with a half life of 8 minutes. if there are 450 grams of element x, how long, to the nearest tenth of a minute, would it take the element to decay to 37 grams?

Lee has $1.75 in dimes and nickels. the number of nickels is 11 more than the number of dimes. how many of each coin does he have?

Is the product of two rational numbers irrational or rational? first, make a hypothesis by multiplying two rational numbers. then, use variables such as x=a/b and y=c/d and the closure property of integers to prove your hypothesis.