1) -2,4m*(-3n)= 2,4m*3n= <u>7,2mn</u>
2) -8а-12b+5а+17b= <u>-3a+5b</u>
3) a-(a+5)+(-7+a)= a-a-5-7+a= <u>-5-7+a</u>
4) -5(y-4)+(y+5)= -5y+20+y+5= <u>-4y+25</u>