Her brother is 7 years old at the moment. He will be 21 when his sister is 36.
Answer:

Step-by-step explanation:

Complete question is in comment section :
Answer:
68%
Step-by-step explanation:
Mean = 25
Standard deviation = 5
The percentage of trees between 20 and 30
20 trees = 1 standard deviation below the mean ; mean - 1(standard deviation)
25 - 5 = 20
30 trees = 1 standard deviation above the mean ;
Mean + 1(standard deviation) ;
25 + 5 = 30
This means, 20 and 30 lies ±1 standard deviation from the mean which according to the empirical rule is 68%
According to the empirical rule :
The answer for your question is 173
Answer:
x=15
Step-by-step explanation:
Since the little square next to A has been cut in half we know that 3x = 1/2 of 90:
3x=45
Divide both sides by 3:
3x÷3=45÷3
x=15