The sum of sally's age plus twice tomas' age is 12. the difference of sally's age and tomas' age is 3. write and solve a system of equations to find their ages.

x represents Sally's age. y represents Thomas's age.

x + 2y = 12

x –y = 3

Step-by-step explanation:

Solve by substitution. Rewrite the second equation to get a value for x.

x -y = 3 Add y to both sides so it becomes x = y+3

Substitute in place of x in the first equation.

x + 2y = 12 becomes

(y + 3) + 2y =12. Combine like terms.

3y + 3 = 12 Subtract 3 from both sides

3y = 12 –3

3y = 9 Divide both sides by 3

y = 3 Tomas

Substitute for y, solve for x

x + 2(3) = 12

x + 6 = 12 Subtract 6 from both sides.

x = 6 Sally

48 / 6 = x

in this case, x will equal the amount of money in each card!

x therefore will be 8.

trent had $8 in each birthday card.