Solve for n
n=10
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420=\left(3+39\right)n
Multiply both sides of the equation by 2.
420=42n
Add 3 and 39 to get 42.
42n=420
Swap sides so that all variable terms are on the left hand side.
n=\frac{420}{42}
Divide both sides by 42.
n=10
Divide 420 by 42 to get 10.
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