@Kirey
A) $\frac{7.25-49}{7.24+21}$
=$\frac{7.25-(7.7)}{7.24+(7.3)}$
=$\frac{7.(25-7)}{7.(24+3)}$
= $\frac{7.18}{7.27}$ = $\frac{2}{3}$
B) $\frac{2.(-13).9.10}{(-3).4.(-5).26}$
=-$\frac{2.13.9.10}{3.4.5.26}$
= -$\frac{(2.10).13.9}{3.(4.5).26}$
=-$\frac{20.13.9}{3.20.26}$ { 20 rút gọn cho 20 ; 13 rút gọn cho 26 : 9 rút gọn cho 3 }
=$\frac{3}{2}$