8/13=2x/39 и 3/14=21/2(x+31) решите

Первый Х=12. Второй Х=18

8/13 = 2х/39
2х = 39•8/13
х = 3•8/2
х = 3•4
х =12

3/14 = 21/2(х+31)
х+31 = 3/14 : 21/2
х+31 = 3/14 • 2/21
х+31 = (3•2)/(14•21)
х+31 =(1•1)/7•7)
х+31 = 1/49
х = 1/49 - 31
х = 1/49 -1519/49
х = -1518/49
х = -30 48/49