So here comes the fun part, Steemkidss have now made maths easy and fun for us kids and i am always so grateful to them for being so considerate about children's mental growth. This will add to our knowledge as algebra has always been my favorite to learn so far.
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What's the difference between Algebraic Expression and Algebraic Equation?

Algebraic expression is a mathematical notation for the coefficients, terms and operations of an algebraic equation. Algebraic equation is an equation that has been expressed in algebraic notation. The most common form of algebraic expression is an equation with one unknown, x. An algebraic equation can also have more than one unknown, as in the equation x + y = 10. Algebraic equation is also used for equations that are not algebraic, such as the equation 3x - 4y = 9. Algebraic expression and algebraic equation are often used interchangeably, but there is a difference.

What's the difference between a coefficient and a constant?

Coefficient: A coefficient is a mathematical term that represents the amount of change in a quantity when one or more other quantities are changed. A coefficient is also called a coefficient of variation, because it tells us how much a quantity varies when its condition is varied.
Constant: A constant is a mathematical term that represents a numerical value that does not change with the conditions of the problem. A constant is also called a constant of variation, because it tells us how much a quantity varies when its condition is varied.

Coefficient

Here in this equation coefficient is 2 that is written with the x.

Represent this as an Algebraic Expression and as an Algebraic Equation.

If we represent pens with x and notebooks with y and he has spent 10$ on it, to represent in the form of algebraic expression we will write
8x+ 5y=10