Answer:
x=\frac{64}{5}=12\frac{4}{5}
Step-by-step explanation:
1. Simplify the expression
\frac{-1}{4}\cdot\left(x+\frac{12}{3}\right)=\frac{+\left(-21\right)}{5}
Find the greatest common factor of the numerator and denominator:
\frac{-1}{4}\cdot\left(x+\frac{\left(4\cdot3\right)}{\left(1\cdot3\right)}\right)=\frac{+\left(-21\right)}{5}
Factor out and cancel the greatest common factor:
\frac{-1}{4}\cdot\left(x+4\right)=\frac{+\left(-21\right)}{5}
Multiply the fractions:
\frac{\left(-1\cdot\left(x+4\right)\right)}{4}=\frac{+\left(-21\right)}{5}
Expand the parentheses:
\frac{\left(-x-4\right)}{4}=\frac{+\left(-21\right)}{5}
Break up the fraction:
\frac{-x}{4}+\frac{-4}{4}=\frac{+\left(-21\right)}{5}
Find the greatest common factor of the numerator and denominator:
\frac{-x}{4}+\frac{\left(-1\cdot4\right)}{\left(1\cdot4\right)}=\frac{+\left(-21\right)}{5}
Factor out and cancel the greatest common factor:
\frac{-x}{4}-1=\frac{+\left(-21\right)}{5}
