Pastry Chef Pierre takes x hours to decorate a wedding cake. Pastry chef Franco takes y hours to decorate a wedding cake. If Pierre works alone for z hours and is then joined by Franco until 20 cakes are decorated, for how long did the two pastry chef's work together.	Select the correct option
A) 20xz-y/(x+y)  B) y+z/(20xz)  C) 20x(y-z)/(x+y)  D) 20xy-z/(x+y)  E) y(20x-z)/(x+y)
time by pierre to complete 1 cake=x   time by franco to complete 1 cake=y   in z hours pierre completes= z/x work   then the both chef guy works together; let the time taken together be t   then we have   (work done by Pierre guy in z hours)+(work done by both guy in t hours)=20   =&gt; (z/x)+(1/x+1/y)*t=20   =&gt; t= (20-(z/x))/(1/x+1/y)=(20x-z)*y/(x+y)   y(20x-z)/(x+y)   20xz-y/(x+y)NSWER:20xz-y/(x+y)
<result>A</result>
Pastry Chef Pierre takes x hours to decorate a wedding cake. Pastry chef Franco takes y hours to decorate a wedding cake. If Pierre works alone for z hours and is then joined by Franco until 20 cakes are decorated, for how long did the two pastry chef's work together.