rho[x_,y_] := x^2 * y

m := Integrate[ rho[x,y], {x,-1,1}, {y,0,1-x^2}]

m

Mx := Integrate[ rho[x,y]*y, {x,-1,1}, {y,0,1-x^2}]

Mx

My := Integrate[ rho[x,y]*x, {x,-1,1}, {y,0,1-x^2}]

My

xBar := My/m

xBar

yBar := Mx / m

yBar