Câu 1 :
a, 136 × 75 + 75 × 64
= ( 136 + 64 ) × 75
= 200 × 75
= 15000
b, ( $\frac{21}{8}$ + $\frac{1}{2}$ ) : $\frac{5}{16}$
= ( $\frac{21}{8}$ + $\frac{4}{8}$ ) : $\frac{5}{16}$
= $\frac{25}{8}$ : $\frac{5}{16}$
= $\frac{25}{8}$ . $\frac{16}{5}$
= 4
Câu 2 :
a, $\frac{2}{3}$x + $\frac{3}{4}$ = 3
$\frac{2}{3}$x = 3 - $\frac{3}{4}$
$\frac{2}{3}$x = $\frac{12}{4}$ - $\frac{3}{4}$
$\frac{2}{3}$x = $\frac{9}{4}$
x = $\frac{9}{4}$ : $\frac{2}{3}$
x = $\frac{9}{4}$ . $\frac{3}{2}$
x = $\frac{27}{8}$
b, 720 : [ 41 - ( 2 x - 50 ) ] = 120
41 - ( 2 x - 50 ) = 720 : 120
41 - ( 2 x - 50 ) = 6
2 x - 50 = 41 - 6
2 x - 50 = 35
2 x = 35 + 50
2 x = 85
x = 85 : 2
x = 42,5
HỌC TỐT NHA !
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