20=h*80*50
$\frac{2x}{3y}$ x $\frac{4y}{5x^2}$
3𝑥−5𝑦−2𝑥−4(2𝑦−7𝑥)
5*(_+3)=25
63-{ ( 24-)×15}
distribute 445400 among 164 in range of 2300,3000,5500,5700,12000
2*3+2*_=14
$\sqrt{\Box}$36+4- $\sqrt{\Box}$ 100-36
+
9