Answer:
<em>Cathy was born in 1980 and she was 18 years old in 1998</em>
Step-by-step explanation:
<u>Equations</u>
This is a special type of equations where all the unknowns must be integers and limited to a range [0,9] because they are the digits of a number.
Let's say Cathy was born in the year x formed by the ordered digits abcd. A number expressed by its digits can be calculated as

In 1998, Cathy's age was

And it must be equal to the sum of the four digits

Rearranging

We are sure a=1, b=9 because Cathy's age is limited to having been born in the same century and millennium. Thus

Operating

If now we try some values for c we notice there is only one possible valid combination, since c and d must be integers in the range [0,9]
c=8, d=0
Thus, Cathy was born in 1980 and she was 18 years old in 1998. Note that 1+9+8+0=18
Quadrilateral the word that describe the equal share of 4 equal sides
Assume the smaller one is x, then the other ones will be x+2 and x+4
x(x+2) + 2 = 5(x+4)
x^2 + 2x - 5x - 18 = 0
-> x^2 - 3x - 18 = 0
-> (x-6)(x+3) = 0
-> x = 6 or -3, since x must be positive, then x = 6
So the numbers are: 6, 8, 10
Answer:
x = 2
,
y = −
3
Step-by-step explanation
Solve for the first variable in one of the equations, then substitute the result into the other equation.
Point Form: (
2
,
−
3
)
Equation Form: x = 2
,
y = −
3