<span>х+х+18 = 66</span>
<span>2х = 66-18</span>
<span>2х = 48</span>
<span>х = 48\2</span>
<span>х = 24</span>
х+х+18=66
2х=66-18
2х=48
х=48/2
х=24
24+24+18=66