The equ is 4x plus 6y eql to 20; 3x plus 4y equl to 28.
By eliminating x variable by using elimination method we get 2y eqlto -52.
Which implies y eql to -26.
On substituting y eql to -26 in equ 4x plus 6y eql to 20, we get: 4x -156 eql to 20.
Which implies x equl to 44.
There fore the time taken by one man alone is 44 and the time taken by one boy alone is -26.