1. 2(x+1)=1-(x-4).
2x+2=1-x+4
3x=3
x=1
2. 1999+999的平方.
= 1999×(1+1999)
=1999×2000
=3998000
3. (2890+5/6+7/8+7/10)除以(5/6+7/8+7/10).
= (2890+5/6+7/8+7/10)×(5/6+7/8+7/10)分之1
=2890×(5/6+7/8+7/10)分之1+(5/6+7/8+7/10)(5/6+7/8+7/10)分之1
=2890×289分之120+1
=1200+1=1201
4. 18%:3/20=x/6.5
3/20x=117/100
x=39/5