# Evaluating expressions in one variable

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The Evaluating expressions in one variable exercise appears under the 6th grade (U.S.) Math Mission and Algebra I Math Mission. This exercise helps in the basic understanding of Algebra.

## Types of problems

1. Evaluate the following expression when ${x}$ = a number - This problem gives the user an expression with an unknown and a number added of subtracted to that unknown ${x}$. The user is to substitute the ${x}$ value into the expression and evaluate it.

## Strategies

1. It is not so easy to get the accuracy badges and speed badges in this exercise. Substituting the ${x}$ into the expression and evaluating it may take some time.

## Real-life Applications

1. Work problems often ask us to calculate how long it will take different people working at different speeds to finish a task. The algebraic models of such situations often involve rational equations derived from the work formula, ${W = rt}$. The amount of work done (${W}$) is the product of the rate of work (${r}$) and the time spent working (${t}$). The work formula has 3 versions:
${W = rt}$
${t = \frac{W}{r}}$
${r = \frac{W}{t}}$
2. Knowledge of algebra is essential for higher math levels like trigonometry and calculus. Algebra also has countless applications in the real world.