1.25×39×8×2=1.25×8×39×2=10×39×2=390×2=780
=(1.25×8)×(39×2)=10×78=780
1.25×39乘以8×2=1.25×8×(39×2)=10×78=780
1.25x8x39x2=10x39x2=780
