Maybe because you're finding the "difference" between the two numbers. We could also question why the answer to an addition problem is called sum.
Well, 'sum'body said that's what they should be called a long time ago, that's why we're using that term to call them now.
Answer:
9 hr * 60 min/hr = 540 min. 540 min * 60 sec/min = 32,400 sec. Use the method described by panic mode: round the number down until there is only one non-zero digit left. Here, 32,400 rounds down to 30,000. Now count the number of zeroes; the result is the order of magnitude: 4. (You see this in scientific notation also: 30,000 = 3 × 10^4.)
Lets Anna's age = A
Mr. Goldstein age = G
Mr. Goldstein is 4 times as old as his daughter Anna.
So G= 4A
In 4 years, he will be 3 times as old as Anna
we add 4 with Both their ages
G + 4 = three times of A + 4
G + 4= 3(A + 4)
We know G= 4A, replace it in above equation
4A + 4= 3(A + 4)
4A + 4= 3A + 12
Subtract 3A from both sides
A + 4 = 12
Subtract 4 from both sides
A = 8
So Anna's age = 8 years
Answer:
Rhe equation would be y= -2x+8
