Solve 20+-1/2-3{left(1/2right)}^2

$$20+- \frac{ 1 }{ 2 } -3 { \left( \frac{ 1 }{ 2 } \right) }^{ 2 }$$

Evaluate

$$\frac{75}{4}=18.75$$

Solution Steps

Convert 20 to fraction \frac{40}{2}.

$$\frac{40}{2}-\frac{1}{2}-3\times \left(\frac{1}{2}\right)^{2}$$

Since \frac{40}{2} and \frac{1}{2} have the same denominator, subtract them by subtracting their numerators.

$$\frac{40-1}{2}-3\times \left(\frac{1}{2}\right)^{2}$$

Subtract 1 from 40 to get 39.

$$\frac{39}{2}-3\times \left(\frac{1}{2}\right)^{2}$$

Calculate \frac{1}{2} to the power of 2 and get \frac{1}{4}.

$$\frac{39}{2}-3\times \frac{1}{4}$$

Multiply 3 and \frac{1}{4} to get \frac{3}{4}.

$$\frac{39}{2}-\frac{3}{4}$$

Least common multiple of 2 and 4 is 4. Convert \frac{39}{2} and \frac{3}{4} to fractions with denominator 4.

$$\frac{78}{4}-\frac{3}{4}$$

Since \frac{78}{4} and \frac{3}{4} have the same denominator, subtract them by subtracting their numerators.

$$\frac{78-3}{4}$$

Subtract 3 from 78 to get 75.

$$\frac{75}{4}$$

Factor

$$\frac{3 \cdot 5 ^ {2}}{2 ^ {2}} = 18\frac{3}{4} = 18.75$$