Which expression represents the sum of 21 and an unknown number?
a. 21-d
b. 21+d
c. 21÷d
d.21d

Four congruent circular holes with a diameter of 2 in. were punches out of a piece of paper. what is the area of the paper that is left ? use 3.14 for pi

Name each raycalculation tip: in ray "ab", a is the endpoint of the ray.

If 2(a^2+b^2)=(a+b)^2 then, > a+b=0, > ab=0, > a=b, > 2a=b