Răspuns:
[156-(90:x+12):3]×2-8=290
=[156-(90:x+12):3]×2=290+8=298
=156-(90:x+12):3=298:2=149
=(90:x+12):3=156-149=7
=90:x+12=7×3=21
=90:x=21-12=9
=x=90:9
x=10