Question

If RS = 3x + 1

and ST = 2x
and RT = 21
what is x and RS?


O x= 20, R$= 8
O x= 4, RS = 8
O x = 4. RS =13
O x= 20. RS = 21

Answer 1

(c) x = 4, RS =13

Explanation:

You want to find x and RS when RS=3x+1, ST=2x, and RT=21.

Solution

As with many multiple-choice problems, the only consistent answer is the correct one.

If x=20, then 3x+1 = RS = 3(20)+1 = 61. This eliminates choices A and D.

If x=4, then 3x+1 = RS = 3(4) +1 = 13. This eliminates choice B and selects choice C.

The correct answer is x=4 and RS=13.

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Working it out

The sum of segment lengths is the total length.

RS +ST = RT

(3x +1) +(2x) = 21

5x = 20 . . . . . . . . . subtract 1

x = 4 . . . . . . . . . . . divide by 5

RS = 3(4) +1 = 13