Justify the last 2 steps. Given: RS=UT and RT=US Prove RST=UTS Proof: 1. RS=UT given 2. RT=US Given 3. ST=TS ? RST=UTS ?

Justify the last 2 steps. Given: RS=UT and RT=US Prove RST=UTS Proof: 1. RS=UT given 2. RT=US Given 3. ST=TS ? RST=UTS ?