Solve for a
a=5
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3a=21-6
Subtract 6 from both sides.
3a=15
Subtract 6 from 21 to get 15.
a=\frac{15}{3}
Divide both sides by 3.
a=5
Divide 15 by 3 to get 5.
Examples
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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]
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\left. \begin{cases} { 8x+2y = 46 } \\ { 7x+3y = 47 } \end{cases} \right.
Differentiation
\frac { d } { d x } \frac { ( 3 x ^ { 2 } - 2 ) } { ( x - 5 ) }
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Limits
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