Question 1: 
<h3>Answer: The number does <u>not</u> change</h3>
Removing the zero from 0.76 leads to .76 which is the same as before. Both lead to  in scientific notation.
 in scientific notation.
Personally I prefer the zero up front to make the decimal point stand out easier. Of course it's just a preference, so its up to you to decide which you prefer.
===========================================
Question 2:
<h3>Answer: Yes the number changes</h3>
Taking the zero out of 10.25 leads to 1.25 which is definitely a different number (and smaller). Therefore, this zero is a significant digit compared to before. 
 
        
             
        
        
        
Answer:
24 miles 
Step-by-step explanation:
Set up a proportion:
3 inches/1.25 miles = x inches/10 miles
Then cross multiply 
30=1.25x
Divide 1.25 on both sides 
x=24
 
        
             
        
        
        
Answer:
4 / 9  probability of getting a red
Step-by-step explanation:
How many marbles are there total?
4 red + 2 yellow + 3 green = 9 marbles total
P( red marble) = 4 red / 9 total = 4/9
 
        
                    
             
        
        
        
Don't panic!  The answer is 42.
But it looks like you did not copy the full question.