64 + 34 : ( x * 3 - 15 ) = 70

65+34:(х*3-15)=70
34:(х*3-15)=70-65
34:(х*3-15)=5
5*(х*3-15)=34
15х-75=34
15х=34+75
15х=109
х=109:15
х=7,3
65+34:(7,3*3-15)=70
65+34:(21,9-15)=70
65+34:6,9=70
65+4,93=70
69,93=70
70=70