hello help me with this question thanks in advance

[tex]\bold{\huge{\underline{ Solution \:1 }}}[/tex]
Here, we
By using basic proportionality theorem :-
That is,
[tex]\sf{\dfrac{ AT}{RT }}{\sf{=}}{\sf{\dfrac{BT}{ST}}}[/tex]
Subsitute the required values,
[tex]\sf{\dfrac{ 8 }{ 8 + 11 }}{\sf{=}}{\sf{\dfrac{7}{7 +10}}}[/tex]
[tex]\sf{\dfrac{ 8 }{ 19}}{\sf{=}}{\sf{\dfrac{7}{17}}}[/tex]
[tex]\sf{\dfrac{ 8 }{ 19}}{\sf{≠}}{\sf{\dfrac{7}{17}}}[/tex]
Hence, AB is not parallel to RS
Here, we have
By using basic proportionality theorem :-
That is,
[tex]\sf{\dfrac{ AT}{RT }}{\sf{=}}{\sf{\dfrac{BT}{ST}}}[/tex]
Subsitute the required values,
[tex]\sf{\dfrac{ 15 }{ 15 + 5 }}{\sf{=}}{\sf{\dfrac{12}{16}}}[/tex]
[tex]\sf{\dfrac{15 }{ 20}}{\sf{=}}{\sf{\dfrac{12}{16}}}[/tex]
[tex]\sf{\dfrac{ 3}{ 4}}{\sf{=}}{\sf{\dfrac{3}{4}}}[/tex]
Hence, AB is parallel to RS
[tex]\bold{\huge{\underline{ Solution\: 2}}}[/tex]
Here, we have
Part 3 :-
By using basic proportionality theorem,
That is,
[tex]\sf{\dfrac{ AD}{AB }}{\sf{=}}{\sf{\dfrac{AE}{AC}}}[/tex]
Subsitute the required values,
[tex]\sf{\dfrac{ 4}{12 }}{\sf{=}}{\sf{\dfrac{AE}{24}}}[/tex]
[tex]\sf{\dfrac{ 4}{12 }}{\sf{{\times} 24= AE}}[/tex]
[tex]\sf{ AE = 4 {\times} 2 }[/tex]
[tex]\sf{ AE = 8 }[/tex]
Hence, The length of AE is 8
Again , By using Basic proportionality theorem :-
That is
[tex]\sf{\dfrac{ AD}{AB }}{\sf{=}}{\sf{\dfrac{DE}{BC}}}[/tex]
Subsitute the required values,
[tex]\sf{\dfrac{ 4}{12 }}{\sf{=}}{\sf{\dfrac{6}{BC}}}[/tex]
[tex]\sf{\dfrac{ 1}{3 }}{\sf{=}}{\sf{\dfrac{6}{BC}}}[/tex]
[tex]\sf{ BC = 6 {\times} 3 }[/tex]
[tex]\sf{ BC = 18 }[/tex]
Hence, The length of BC is 18 .