Solution: If Master Zhang makes a coat in 2x days, then he makes a pair of trousers in (19-2x) days, while Master Wang makes a coat in 3y days and a pair of trousers in (19-y) days.
Because a suit consists of a coat and a pair of trousers.
2x+3y = 2x( 19-2x)+ 19-y
5x+4y=57
x+y=57-x/4
X+y must be an integer.
Therefore, when x= 1, the maximum value of x+y is 14.