1) 8 - 6 1/4 = 7 4/4 - 6 1/4 = 1 3/4
2) 1 3/4 : ( - 5/9 ) = 7/4 : ( - 5/9 ) = - ( 63/20 ) = - 3 ( 3/20 )
3) - 1/2 + 2/5 = - 5/10 + 4/10 = - 1/10
4) 9 * ( - 1/10 ) = - 9/10
5) - ( 63/20 ) - ( - 9/10 ) = - 63/20 + 18/20 = - 45/20 = - 2 ( 5/20 ) = - 2 ( 1/4 ) = - 2,25