Solve for n
n=\frac{7r-15}{4}
Solve for r
r=\frac{4n+15}{7}
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9n+15=5n+7r
Combine 4n and 5n to get 9n.
9n+15-5n=7r
Subtract 5n from both sides.
4n+15=7r
Combine 9n and -5n to get 4n.
4n=7r-15
Subtract 15 from both sides.
\frac{4n}{4}=\frac{7r-15}{4}
Divide both sides by 4.
n=\frac{7r-15}{4}
Dividing by 4 undoes the multiplication by 4.
9n+15=5n+7r
Combine 4n and 5n to get 9n.
5n+7r=9n+15
Swap sides so that all variable terms are on the left hand side.
7r=9n+15-5n
Subtract 5n from both sides.
7r=4n+15
Combine 9n and -5n to get 4n.
\frac{7r}{7}=\frac{4n+15}{7}
Divide both sides by 7.
r=\frac{4n+15}{7}
Dividing by 7 undoes the multiplication by 7.
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Linear equation
y = 3x + 4
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Matrix
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Simultaneous equation
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Differentiation
\frac { d } { d x } \frac { ( 3 x ^ { 2 } - 2 ) } { ( x - 5 ) }
Integration
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Limits
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