phillll 1)(5.3+a)-(a+6.4)=5.3+a-a-6.4=-1.1
2)-(9.4-b)+(-b+3.7)=-9.4+b-b+3.7=-5.7
3)-(x-5.8-y)-(11.3-x)=-x+5.8+y-11.3+x=-5.5+y
4)-(a-b-7.4)+(-7.4+b+a)=-a+b+7.4-7.4+b+a=b