Answer:
SR=15units
‹RTQ=90° since ‹RTQ and ‹RTS are supplementary
Given that ‹RTQ is a right angle then RTQ is a right-angled triangle making RQ the hypotenuse
With that knowledge we calculate RT using Pythagorean theorem
RT=√(20)²-(16)²
RT=√400-256
RT=√144=12units
Now for triangle RST, SR is the hypotenuse and should have the longest length whose adjacent,ST should also sum up with 16 to give a number which when combined will give the square root of the sum of the squares of RQ and SR
Plug in 9 for ST and SR becomes
√(12)²+(9)²=√144+81=√225=15 units
This is true because SQ=16+9=25 units
and using Triangle RSQ,
SQ=√(20)²+(15)²=√400+225=√625=25 units