There are two variables in this situation: your age, and your sister's age. Your age will be known as x, and your sister's will be known as y.
Now you can put the given information into equation form:
Your age = Twice your sister's age
x = 2y
One year from now, your sister will be 3 times your age minus thirteen years.
y + 1 = 3(x - 13)
Since x is clearly the same as 2y, you can substitute that into the second equation, then solve.
y + 1 = 3(2y - 13) --- Substitute 2y
y + 1 = 6y - 39 --- Distribute 3
y + 40 = 6y --- Move constants to one side and add
40 = 5y --- Move variables to one side and add
8 = y --- Divide
Your sister is 8 years old. Now, to find your age, simply set y = 8 in the first equation and solve.
x = 2(8) = 16
You are 16 years old.
Mary is dead
12,4...16,8
Mary is 4 years old. [A+]
There are two possible (and different) answers: 2x + 3y = 12 or 2*(x + 3y)= 12 The first one is (twice a number) increased by (three times another) The second is twice (a number increased by (three times another)).
0.4286 times.
Mary is dead
12,4...16,8
Amy will be 16 when she is twice as old as Emily at 8.
Mary is 4 years old. [A+]
twice the difference of three times a number and eight
Sister = 5 David = 13
Zoron will be seventeen and his sister will be seven
There are two possible (and different) answers: 2x + 3y = 12 or 2*(x + 3y)= 12 The first one is (twice a number) increased by (three times another) The second is twice (a number increased by (three times another)).
0.4286 times.
She had three children and got married twice.
The AED may shock once, twice, or three times.
Mike is 12. Mary is 4. In 4 years, Mike will be 16 and Mary will be 8. So Mike will be twice as old as she is in four years.