$\text { Đáp án: }$
75% + $\frac {3}{4}$ × 29 + 75% × 30 + 0,75 × 40
$\text {= 0,75 + }$ $\frac {3}{4}$ $\text { × 29 + 0,75 × 30 + 0,75 × 40}$
$\text {= 0,75 × (1 + 30 + 40) +}$ $\frac {3}{4}$ $\text {× 29}$
$\text {= 0,75 × 71 + 21,75 }$
$\text {= 53,25 + 21,75 }$
$\text {= 75. }$