The given Equations are RS= 2x+10 (1)

ST= x-4 (2)

RT= 21 (3)

Multiply (1) and (2) to get RTS²= (2x+10)(x-4). Since RT =21

S²= (2x+10)(x-4)/21

Or, S =

Using this value of S in (2) T=

Using the value of T in (3) R=

These are the required solutions for R, S and T in terms of x.

Using these solutions RS= 2x+10 and ST= x-4

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