The triangle on the left has a perimeter of 14, the triangle on the right has a perimeter of 21. What are x and y? Show your steps. I could sit here and figure it out by guessing and substituting, but I'm assuming there is a formula to this, so help?

Question

anonymous · Answer

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jim_thompson5910 · Answer

The left triangle has a perimeter of 14, so

x+y+y = 14

x+2y = 14

solve for x to get

x = -2y + 14

jim_thompson5910 · Answer

the triangle on the right has a perimeter of 21, so

3x+(5/4)y+(5/4)y = 21

12x+5y+5y = 84 ... multiply everything by the LCD 4 to clear out the fractions

12x+10y = 84

12(-2y+14) + 10y = 84 ... plug in x = -2y + 14

Now solve for y

anonymous · Answer

y = 6

anonymous · Answer

Do I plug that in back at the same equation where I plugged in the other, then solve for x?

jim_thompson5910 · Answer

yes, you plug it into x = -2y + 14 to find x

anonymous · Answer

Thank you so much I've been working at this for hours!!