ANSWER
The system of equations are,
and
EXPLANATION
Let J = John's age and M = Mary's age
The first statement says,
"John is twice as old as Mary."
We can write this mathematically as,
or
The second statement says,
"the sum of their ages is 21." Mathematically, we can write this one too as,
The system of equations are,
and
EXPLANATION
Let J = John's age and M = Mary's age
The first statement says,
"John is twice as old as Mary."
We can write this mathematically as,
or
The second statement says,
"the sum of their ages is 21." Mathematically, we can write this one too as,