Which expression represents 81 decreased by an unknown number?

a. 81−a

b. 81a

c. 81÷a

d. 81 + a

Choice A

Step-by-step explanation:

The correct answer is choice A. The equation 81 - a is doing exactly what the question is asking for. It represents 81 minus an unknown number, with the unknown number being shown as a.

The answer is A. 81 - a

Step-by-step explanation: decreased is practically a synonym for subtract, so we use the symbol for subtraction (-). 81 decreased by an unknown number, which then we use a symbol to show the unknown variable, like a letter. So (a) represents the unknown number. Hence, 81 decreased by an unknown number becomes 81 - a.

answer: 0+0=0

step-by-step explanation:

that is the only answer that can make 0

the simplified form is

step-by-step explanation:

we want to simplify the expression,

let us change the middle bar to a normal division sign to obtain,

we multiply the first fraction by the reciprocal of the second fraction to obtain,

we factor to obtain,

we cancel the common factors to get,

we simplify to get,

the correct answer is b