a)
(580-20:2×4):25+550<600=
=(590-10×4):25+550
=(590-40):25+550
=550:25+550
=22+550
=572<600 ESTE ADEVARAT
b)
300-2×[5×(70-26)]:8<250
=300-2×[5×44]:8
=300-2×220:8
=300-440:8
=300-55
=245 <250 ESTE ADEVARAT
c)[(3+47+50):4+91]:2<50
=[100:4+91]:2
=[25+91]:2
=116:2
=58 <50 ESTE FALS
d)[100×(25+50×4)+500)]:10<3000
=[100×725]:10
=72500:10
=7250 <3000 ESTE FALS
SUCCES!