Answer: SAS Similarity theorem.
Explanation.
SAS stands for Side - Angle - Side.
SAS theorem states that if two triangles have
corresponding angles that are congruent and corresponding sides
with identical ratios, then the triangles are similar.
And that is what the figure shows:
1) The angle at M is the same for both triangles.
2) The ratios of the sides are: 2/3 and 4 /6. Given that 2/3 = 4/6 you have that the two corresponding sides have identical ratios.
Answer
Find out the what fraction of the sandcastle did they build together .
To prove
Let us assume that the fraction of the sandcastle they build together be x .
As given


Than the equation becomes

L.C .M of (3,7) = 21
solving


Therefore the fraction of the sandcastle did they build together be

Hence proved
Answer:
18 is the GCF for 18 and 54