What is a variable?
a.
a variable is an unknown number or value represented by a letter
c.
a variable represents a change in value
b.
a variable always represents the total amount
d.
a variable is always represented by the letter x

Three numbers x, y, and z are in the ratio 2: 7: 8. if 12 is subtracted from y, then three numbers form a geometric sequence (in the order x, y–12, z). find x, y, and z. there are 2 sets.

Suppose a laboratory has a 30 g sample of polonium-210. the half-life of polonium-210 is about 138 days how many half-lives of polonium-210 occur in 1104 days? how much polonium is in the sample 1104 days later? 9; 0.06 g 8; 0.12 g 8; 2,070 g

With this problem-elena cycled to school. find the distance travelled by elena if her bicycle wheels rotated 840 times and the radius is 0.25 m.