Can someone help me solve #3 and it needs to be a 6th grade type answer? I will put you as brainliest if you can solve also I need an explanation of you don’t mind. I need this answered correctly ASAP

Answer:
Step-by-step explanation:
{4 (g-h)+10 g = 12, h = 7}
4 (12-7)+10
4*5+10
20+10
30
Answer:
24
Step-by-step explanation:
8-2z + 3[x + y] ,when x=4, y=9, z=3
8-23 + 3[4 + 9]
8-23= -15
3[4 + 9]= 39
-15+39=24
your answer is 24