X -1.8=4 X - 2=15 1.6X=6.4 X÷7=0.3 X÷3=2.1用关系式怎么解

X -1.8=4
两边同时加上1.8
X-1.8+1.8=4+1.8
X=5.8
X - 2=15
两边同时加上12
X-2+2=15+2
X=17
1.6X=6.4
两边除以1.6
1.6X÷1.6=6.4÷1.6
X=4
X÷7=0.3
两边乘以7
X÷7×7=0.3×7
X=2.1
X÷3=2.1
两边乘以3
X÷3×3=2.1×3
X=6.3