①5/11-x=1/5
x=5/11-1/5
x=25/55-11/55
x=14/55
②x-7/12=7/18
x=7/12+7/18
x=21/36+14/36
x=35/36
③x-7/19=7/19
x=7/19+7/19
x=14/19
④3/14+x=1/2
x=1/2-3/14
x=7/14-3/14
x=4/14
x=2/7