#### Answer

a. 2x
b. 8+x
c. 10-x
d. x-10
e. $6 \div x$ or $\frac{6}{x}$

#### Work Step by Step

a. Twice a number is another way of saying 2x
b. 8 increased by an unknown number is written as 8+x
c. 10 decreased by an unknown number is written as 10-x
d. 10 subtracted from a number is written as x-10
e. To write the quotient of 6 and a number, you can write it as an expression with the dividing sign or as a fraction. . $6 \div x$ or $\frac{6}{x}$