10: x=5, a × 2=10, 2 × x=10, a:2=5.

10 : х = 55х = 10х = 10 : 5х = 2--------------------а* 2 = 102х = 10х = 10 : 2х = 5-------------------------2* х = 102х = 10х = 10 : 2х = 5---------------------------а : 2 = 5а = 5 * 2а = 10