6.2x+x=14.4 解:7.2x=14.4 7.2x÷7.2=14.4÷7.2 x=2 3x-1.2=10.8 解:3x-1.2+1.2=10.8+1.2 3x=12 3x÷3=12÷3 x=4 3(x+0.2)=0.96 解:3(x+0.2)÷3=0.96÷3 x+0.2=0.32 x+0.2-0.2=0.32-0.2 x=0.12 13×(x+5)=169 解:13×(x+5)÷13=169÷13 x+5=13 x+5-5=13-5 x=8 (10+x)÷5.4=2.5 解:(10+x)÷5.4×5.4=2.5×5.4 10+x-10=13.5-10 x=3.5 7x-4.2=9.8 解:7x-4.2+4.2=9.8+4.2 7x=14 7x÷7=14÷7 x=2 (x-3)÷2=7.5 解:(x-3)÷2×2=7.5×2 x-3=15 x-3+3=15+3 x=18 8(x+2.8)=50.4 解:8(x+2.8)÷8=50.4÷8 x+2.8=6.3 x+2.8-2.8=6.3-2.8 x=3.5