What is the missing number in the equation?

3/10 x ? = 21/10

7 , or 7/1

Step-by-step explanation:

Let ? = x. Set the equation:

(3/10)x = 21/10

Isolate the variable, x. Multiply 10/3 to both sides of the equation:

x * (3/10) * (10/3) = (21/10) * (10/3)

x = 21/10 * 10/3

Simplify the equation. Divide common factors from both the numerator and denominator, and then simplify:

x = (21 * 10)/(10 * 3)

x = (21/3) = 7/1 = 7

x = 7