一、计算 89-4= 76-5= 54-30= 68-40= 77-40= 67-30= 68-30= 26-4= 85-70= 46-6= 73-50= 87-3= 99-7= 56-3= 72-20= 27-7= 95-70= 44-30= 58-40= 48-3= 48-30= 57-6= 47-6= 58-30= 75-3= 75+3= 34-3= 87-6= 74-2= 78-60= 34-30= 78-6= 74+2= 74-20= 75-3= 88-5= 56-4= 89-7= 46-20= 69-40= 38-7= 68-5= 47-3= 75-20= 86-5=