(5,75-6,9)-(1/4+1/10)

1) ( 5,75-6,9)-(1/4+1/10)= (-1,15)-(5/20+2/20)=(-1 15/100) - 7/20=(-1 3/20)-7/20= -1 10/20= - 1 1/2 = -1,5.