Bài làm:
b) (1$\frac{2}{25}$ + $\frac{14}{9}$ + $\frac{17}{5}$ ) - ($\frac{2}{25}$ + $\frac{5}{9}$ + 40%)
= (1$\frac{2}{25}$ + $\frac{14}{9}$ + $\frac{17}{5}$ ) - ($\frac{2}{25}$ + $\frac{5}{9}$ + $\frac{2}{5}$ )
= 1$\frac{2}{25}$ + $\frac{14}{9}$ + $\frac{17}{5}$ - $\frac{2}{25}$ - $\frac{5}{9}$ - $\frac{2}{5}$
= ( 1$\frac{2}{25}$ - $\frac{2}{25}$ ) + ( $\frac{14}{9}$ - $\frac{5}{9}$ ) + ( $\frac{17}{5}$ - $\frac{2}{5}$)
= 1 + $\frac{9}{9}$ + $\frac{15}{5}$ = 1 + 1 + 3 =5
c) ( $\frac{2525}{2727}$ × $\frac{272727}{292929}$ )×$\frac{32}{y-2007}$ = 1$\frac{1}{7}$ × $\frac{50}{29}$
⇒ ($\frac{25×101}{27×101}$ × $\frac{27×10101}{29×10101}$)×$\frac{32}{y-2007}$ = $\frac{8}{7}$ ×$\frac{50}{29}$
⇒ ( $\frac{25}{27}$ × $\frac{27}{29}$ ) × $\frac{32}{y-2007}$ = $\frac{8}{7}$ × $\frac{50}{29}$
⇒ $\frac{25}{29}$ × $\frac{32}{y-2007}$ = $\frac{8}{7}$ × $\frac{50}{29}$
⇒ $\frac{32}{y-2007}$ = $\frac{8}{7}$ × $\frac{50}{29}$ : $\frac{25}{29}$
⇒ $\frac{32}{y-2007}$ = $\frac{8}{7}$ × $\frac{50}{29}$ × $\frac{29}{25}$
⇒ $\frac{32}{y-2007}$ = $\frac{16}{7}$ = $\frac{32}{14}$
⇒ y-2007 = 14 ⇒ y = 2007 + 14 = 2021
Đáp số: y = 2021
