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Bài 1:
\(\dfrac{2}{3}\) + \(\dfrac{3}{4}\) - \(\dfrac{2}{5}\)
=\(\dfrac{40}{60}\) + \(\dfrac{45}{60}\) - \(\dfrac{24}{60}\)
= \(\dfrac{61}{60}\)
b; \(\dfrac{12}{13}\) x \(\dfrac{3}{4}\) - \(\dfrac{7}{13}\)
= \(\dfrac{9}{13}\) - \(\dfrac{7}{13}\)
= \(\dfrac{2}{13}\)
c; \(\dfrac{15}{17}\) : \(\dfrac{19}{34}\) - \(\dfrac{17}{19}\)
= \(\dfrac{15}{17}\) x \(\dfrac{34}{19}\) - \(\dfrac{17}{19}\)
= \(\dfrac{30}{19}\) - \(\dfrac{17}{19}\)
= \(\dfrac{13}{19}\)
Bài 2:
a; \(\dfrac{x}{5}\) x \(\dfrac{3}{7}\) = \(\dfrac{9}{35}\)
\(\dfrac{x}{5}\) = \(\dfrac{9}{35}\) : \(\dfrac{3}{7}\)
\(\dfrac{x}{5}\) = \(\dfrac{3}{5}\)
\(x\) = \(\dfrac{3}{5}\) x 5
\(x\) = 3
A. \(\frac{4}{5}\times\frac{8}{3}\times\frac{x}{7}=\frac{96}{105}\)
=\(\frac{4}{5}\times\left(\frac{8}{3}\times\frac{x}{7}\right)=\frac{96}{105}\)
= \(\frac{8}{3}\times\frac{x}{7}=\frac{96}{105}\div\frac{4}{5}\)
= \(\frac{8}{3}\times\frac{x}{7}=\frac{480}{420}=\frac{8}{7}\)
=\(\frac{x}{7}=\frac{8}{7}\div\frac{8}{3}\)
= \(X=\frac{24}{56}=\frac{3}{7}\)
\(X=3\)
@Moon
( 5 x 6 + 7 - 37 ) x ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 )
= ( 30 + 7 - 37 ) x ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 )
= 37 - 37 x ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 )
= 0 x 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10
= 0
( 5 x 6 + 7 - 37 ) x ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 )
= 0 x ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 )
= 0
\(7\times3+\frac{9}{2}\)
\(=21+\frac{9}{2}\)
\(=\frac{42}{2}+\frac{9}{2}\)
\(=\frac{51}{2}\)
7 × 3 + 9/2
= 21 + 4,5
= 25,5