Two Unknowns for Kids: Systems of Equations Word Problems (Grade 8 Math)

Hi, I'm Luna from DoodleBeez. Today we are solving word problems with two unknowns. When two things are mystery numbers, we need two clues. Together, the two clues let us find both numbers.

Two numbers add up to twenty. The bigger one is four more than the smaller one. Take away the difference first. Twenty minus four is sixteen. Half of sixteen is eight, so the numbers are eight and twelve.

Check the answer with both clues. Eight plus twelve is twenty. Twelve minus eight is four. Both clues work, so we know the answer is right.

One adult ticket and one child ticket cost thirteen dollars. Two adult tickets and one child ticket cost twenty one dollars. The second list has one extra adult, so one adult ticket is twenty one minus thirteen, which is eight dollars.

Now use the first clue to find the child ticket. One adult and one child cost thirteen dollars. The adult ticket is eight dollars, so the child ticket is thirteen minus eight, which is five dollars.

Here is a trickier one. Three pens and two pencils cost eleven dollars. One pen and two pencils cost five dollars. The difference is two pens, which cost six dollars, so one pen costs three dollars and one pencil costs one dollar.

Now it's your turn. Two apples and one banana cost seven dollars. One apple and one banana cost four dollars. What does one apple cost? Pause and try. The extra apple costs seven minus four, which is three dollars. The banana costs one dollar.

Great job! Remember, two unknowns need two clues. Compare the clues to find one number, then use it to find the other. Always check your answers in both clues. Practice two unknowns in Middle School Math at doodlebeez.com. See you next time!