91影视

A constant is a number like$1,2,10.5,$ etc. A variable is a letter or a literal used to signify an unknown quantity.

When a constant is multiplied by a variable we just append the constant in front of the variable.

We are given a constant $5$ and a variable $x$, so their product will be $5x$

Like terms are the terms having same variables and raised to the same index. Coefficient is the appended number in front of the variable; if no number is shown then we assume it to be 1.

For example 4x and 5x are like terms.

Unlike terms are the terms not having same variables and or are raised to the different index.

For example 4 and 5x are unlike terms.

We can add like terms by adding their coefficients, we cannot add unlike terms.

Now 5 times a number$x$ is$5x$ and we add 3 to it to obtain

$5x+3$

We have been given that the sum$5x+3$is the same as 15 thus, we have

$5x+3=15$

Thus, the required equation is $5x+3=15$.