(1)3×2.8+2×1.8,
=8.4+3.6,
=12(元),
答:买3千克茄子2千克西红柿需要12元;
(2)做西红柿炒黄瓜,需要买0.5千克西红柿和0.5千克黄瓜,
1.8×0.5+2.4×0.5,
=0.9+1.2,
=2.1(元),
答:需要2.1元.
(1)3×2.8+2×1.8,
=8.4+3.6,
=12(元),
答:买3千克茄子2千克西红柿需要12元;
(2)做西红柿炒黄瓜,需要买0.5千克西红柿和0.5千克黄瓜,
1.8×0.5+2.4×0.5,
=0.9+1.2,
=2.1(元),
答:需要2.1元.