(2+х:7)*8=72
(2+х:7)=72:8
(2+х:7)=9
х:7=9-2
х:7=7
х=7*7=49
(2+49:7)*8=72
35:(15-Y:8)=5
(15-Y:8)=35:5=7
Y:8 =15-7=8
Y:8=8
Y=8*8=64