## Algebra 1

Let both mark and lynn clean the office in $T$ minutes together. (Fraction work done in a minute by Karen)+ (Fraction work done in a minute by kim)=1 $\implies (\dfrac{1}{15}+\dfrac{1}{10})T=1$ $\implies (\dfrac{2+3}{30})T=1$ $5T=30$ or, $T=6$ minutes