<span>340+? +120=<span> 460+ ?</span></span>
<span><span><span> ? -360 -120 =<span>? -460</span></span></span></span>
<span><span><span><span>360 -120 +? =<span> 240+?</span></span></span></span></span>
<span><span><span><span><span><span>360 -120 -? =<span>240 -?</span></span></span></span></span></span></span>
<span><span><span><span><span><span><span><span> 120 +360 -? =<span> 460-?</span></span></span></span></span></span></span></span></span>