Answer:
a) Here we have:
"In Family A, the youngest child is 7 years younger than the oldest, who is 18"
Let's define:
Y = age of the youngest child.
O = age of the oldest child.
Then we know that:
Y = O - 7
O = 18
Then we can replace the second equation into the first one:
Y = 18 - 7 = 11.
b) Here we have:
"In Family B, the middle child is 5 years older than the youngest child."
Let's define:
Y = age of the youngest child.
M = age of the middle child.
Here we have only one equation:
M = Y + 5.
Answer:
Juan has to work at least 21 weeks.
Step-by-step explanation:
Juan earns $3 a day, then he earns $21 per week.
Let x be the number of weeks Juan works. He will earn $21x in x weeks.
Juan has saved $213,
He earns $21x,
Juan's total earnings are $213+$21x.
He needs to save at least $654, so

Juan has to work at least 21 weeks.
Answer:
3x-4y=-16
Step-by-step explanation:
<span>A. Sally, Bob, and Javier ride the bus every day.</span>