Solve for x
x = \frac{7}{5} = 1\frac{2}{5} = 1.4
Graph
Share
Copied to clipboard
3x-21+12x=0
Add 12x to both sides.
15x-21=0
Combine 3x and 12x to get 15x.
15x=21
Add 21 to both sides. Anything plus zero gives itself.
x=\frac{21}{15}
Divide both sides by 15.
x=\frac{7}{5}
Reduce the fraction \frac{21}{15} to lowest terms by extracting and canceling out 3.
Examples
Quadratic equation
{ x } ^ { 2 } - 4 x - 5 = 0
Trigonometry
4 \sin \theta \cos \theta = 2 \sin \theta
Linear equation
y = 3x + 4
Arithmetic
699 * 533
Matrix
\left[ \begin{array} { l l } { 2 } & { 3 } \\ { 5 } & { 4 } \end{array} \right] \left[ \begin{array} { l l l } { 2 } & { 0 } & { 3 } \\ { -1 } & { 1 } & { 5 } \end{array} \right]
Simultaneous equation
\left. \begin{cases} { 8x+2y = 46 } \\ { 7x+3y = 47 } \end{cases} \right.
Differentiation
\frac { d } { d x } \frac { ( 3 x ^ { 2 } - 2 ) } { ( x - 5 ) }
Integration
\int _ { 0 } ^ { 1 } x e ^ { - x ^ { 2 } } d x
Limits
\lim _{x \rightarrow-3} \frac{x^{2}-9}{x^{2}+2 x-3}