Tính b) –21,25 + 13,3.

a) $\left(-7\right)-\left(\frac{-5}{8}\right)=-7+\frac{5}{8}=\frac{-56}{8}+\frac{5}{8}=\frac{-51}{8}.$

b) –21,25 + 13,3 = –(21,25 – 13,3) = –7,95.