Упростите выражение и найдите его значение:
-6a+7b+3a-4b,если a=0.1
 Помогите пожалуйста объяснить и решить)

2. Fill the gaps with a, an, or some where necessary.
1 a) We had ...some... delicious food last night,
b) We had ...a... delicious meal last night.
2 a) There is … beautiful furniture in that shop,
b) There is … beautiful table in that shop.
3 a) I'm thirsty. I need … drink.
b) I'm thirsty. I need … water.
4 a) She's just bought … expensive clothes.
b) She's just bought … expensive dress.
5 a) They booked … room in advance.
b) They booked … accommodation in advance
6 a) The band played … lovely song.
b) The band played … lovely music.
7 a) We had … heatwave last week.
b) We had … hot weather last week.
8 a) I can't do this job alone. I need … assistant
b) I can't do this job alone. I need … help.
9 a) He has got … heavy luggage to carry.
b) He has got … heavy suitcase to carry.
10 a) I need … cutlery to eat this food with.
b) I need … knife and fork to eat this food with.
11 a) She has got … important job to do.
b) She has got … important work to do.
12 a) He found … coin on the ground.
b) He found … money on the ground