Solve for x
x=9
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3\times 21=7x
Variable x cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by 3x, the least common multiple of x,3.
63=7x
Multiply 3 and 21 to get 63.
7x=63
Swap sides so that all variable terms are on the left hand side.
x=\frac{63}{7}
Divide both sides by 7.
x=9
Divide 63 by 7 to get 9.
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