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put this solution on YOUR website!1. The sum of the ages of two friends is 60.
x + y = 60
y = (60-x)
;
three times the age of one friend is 9 less than four times the age of the other,
3x = 4y - 9
:
how old is each?
:
Substitute (60-x) for y in the above equation:
3x = 4(60-x) - 9
3x = 240 - 4x - 9
:
3x + 4x = 240 - 9
:
7x = 231
x =
x = 33 yrs old
then
60 - 33 = 27 yrs old
;
:
Check solution in the statement:
three times the age of one friend is 9 less than four times the age of the other,
3(33) = 4(27) - 9
99 = 108 - 9
:
:
2. Rolly is twice as old as his brother, Darwin.
r = 2d
:
In five years, Darwin will be the same age as his brother ten years ago.
d + 5 = r - 10
d = r - 10 - 5
d = r - 15
:
What are their present ages?
:
Substitute 2d for r in the above equation
d = 2d - 15
d - 2d = -15
-d = -15
d = 15 yrs is Darwin's present age
then
2(15) = 30 yrs is Roll's present age
:
Check solution in statement:
In five years, Darwin will be the same age as his brother ten years ago.
15 + 5 = 30 - 10
