[latex]42:1 \frac{3}{4} -15,6+1 \frac{2}{3} [/latex]

42×3/4-15.6+2/3 21×3/2-15.6+2/3 21×3/2-15.6+2/3 63/2-15.6+2/3 63/2-156/10+2/3 5×63-2×78/10+2/3 315-2×78/10+2/3 315-156/10+2/3 159/10+2/3 3×159+10×2/30 477+10×2/30 477+20/30=497/30 16×17/30