39.98×26+19.99×74-199.9×2.6
=19.99×2×26+19.99×74-19.9.9×26
=19.99×(2×26+74-26)
=19.99×(26+74)
=19.99×100
=199919.9.9×26???19.9.9(是19.99）×2639.98×26+19.99×74-199.9×2.6 =19.99×2×26+19.99×74-19.99×26 =19.99×(2×26+74-26) =19.99×(26+74) =19.99×100 =1999嗯、帮了大忙了、3Q、