Bài 1:
$\ 41,1 - 0,8 × x = 5,68$
$\ 0,8 × x = 41,1 - 5,68$
$\ 0,8 × x = 35.42$
$\ x = 35,42 : 0.8$
$\ x = 44,275$
Vậy $\ x = 44,275$
Bài 2:
a) $\ \dfrac{5 - 4}{4×5} + \dfrac{6-5}{5×6} + \dfrac{7-6}{6×7}$
$\ = \dfrac{1}{4×5} + \dfrac{1}{5×6} + \dfrac{1}{6×7}$
$\ = \dfrac{1}{4} - \dfrac{1}{5} + \dfrac{1}{5} - \dfrac{1}{6} + \dfrac{1}{6} - \dfrac{1}{7}$
$\ = \dfrac{1}{4} - \dfrac{1}{7}$
$\ = \dfrac{7}{28} - \dfrac{4}{28}$
$\ = \dfrac{3}{28}$
b) $\ 2,15 × 22,06 + 21,5 × 7,694 + 2,15$
$\ = 2,15 × 22,06 + 2,15 × 10 × 7,694 + 2,15$
$\ = 2,15 × 22,06 + 2.15 × 76,94 + 2,15 × 1$
$\ = 2,15 × (22,06 + 76,94 + 1)$
$\ = 2,15 × 100 = 215$
