1.20÷10=2
2+15=17
17×4=68
68-9=59岁
2.222×198-444×49
=222×198-222×98
=222×(198-98)
=222×100
=22200
3.平均成绩=(1×98+3×92+4×86+2×76)÷(1+3+4+2)=870÷10=87分
1.20÷10=2
2+15=17
17×4=68
68-9=59岁
2.222×198-444×49
=222×198-222×98
=222×(198-98)
=222×100
=22200
3.平均成绩=(1×98+3×92+4×86+2×76)÷(1+3+4+2)=870÷10=87分