I am having difficulty differentiating the following questions

1. x^(2/3)+y(2/3)=5 This is what I did

(2/3)x^(-1/3)+(2/3)y^(-1/3) I am also supposed to plot the point(8,1) to find slope

2. tan(x+y)=x This is what I did

sec^2(x+y)(1+1)=1 ? (is this correct?)

3. y=sin(xy)

1=cos(xy)(1y+1x) is this correct?