The equations $\frac{2}{3} x + \frac{3}{2} y = 5$ and $\ldots \ldots \ldots$ are the same.

Solve the following pairs of equations by cross-multiplication method:
$3x - 4y = 17$
$4x - 5y = 21$

The solution of the pair of equations $x + 2y = 5$ and $2x + y = 4$ is .........

Two years ago,the sum of the ages of a mother,father,and two daughters was $40$ years. After three years,what will be the sum of their ages?

The solution of a pair of equations $y+x=2$ and $y-x=4$ is $(x, y)=\ldots \ldots \ldots . . .$

The angles of a cyclic quadrilateral $ABCD$ are $\angle A = (6x + 10)^{\circ}$,$\angle B = (5x)^{\circ}$,$\angle C = (x + y)^{\circ}$,and $\angle D = (3y - 10)^{\circ}$. Find $x$ and $y$,and hence the values of the four angles.