3 is right. The others are wrong.
Please note that a minus sign is - not _
Combine like terms to simplify the expression.
1/_4+6+9y=
Answer: 5y+6
2/ 20a+7+3=
Answer: 20+10
3/_5k+9_2+9k=
Answer: 4k+7
4/ 17+2.9h+3=
Answer: 30+14
Simplify the expression.
5/ _4(3+d)+7d_d=
Answer: _16+6d
6/ 8+5(j_5)+3j_1=
Answer: 32+8j_1
7/ 9(b_3)+4(b_5)=
Answer: 5b+22
8/ _2(2g_6)+4(g_3)=
Answer:zero+9
2 answers
Try using the minus (-) sign for subtraction, not the underscore (_)!
Anyway, you got them almost all wrong:
-4+6+9y = 2+9y (since 6-4=2)
20a+7+3 = 20a+10
-5k+9-2+9k = 4k+7 OK
17+2.9h+3 = 20+2.9h
-4(3+d)+7d-d = -12-4d+7d-d = -12+2d
8+5(j-5)+3j-1 = 8+5j-25+3j-1 = 8j-18
9(b-3)+4(b-5) = 9b-27+4b-20 = 13b-47
-2(2g-6)+4(g-3) = -4g+12+4g-12 = 0
Anyway, you got them almost all wrong:
-4+6+9y = 2+9y (since 6-4=2)
20a+7+3 = 20a+10
-5k+9-2+9k = 4k+7 OK
17+2.9h+3 = 20+2.9h
-4(3+d)+7d-d = -12-4d+7d-d = -12+2d
8+5(j-5)+3j-1 = 8+5j-25+3j-1 = 8j-18
9(b-3)+4(b-5) = 9b-27+4b-20 = 13b-47
-2(2g-6)+4(g-3) = -4g+12+4g-12 = 0