\(a,A=\left(-87,5\right)+\left\{\left(87,5\right)+\left[3,8+\left(-0,8\right)\right]\right\}\)
\(
A=-87,5+87,5+3,8-0,8\)
\(A=\left(-87,5+87,5\right)+\left(3,8-0,8\right)\)
\(A=0+3\)
\(A=3\)
\(b,B=\left[9,5+\left(-13\right)\right]+\left[\left(-5\right)+8\right]\)
\(B=\left(-3,5\right)+3,5\)
\(B=0\)
Chúc bạn học tốt