You know that ABC ~ DEF. The '~' essentially means that the two triangles are similar.
Similar triangles are in proportion. For example, if I had two similar triangles in which one side was 1 cm and the other 2 cm, we would know that the ratio was 1:2.
In this scenario, the side AB ~ DE. We know that the two triangles are in proportion 1:3, because that's the simplified version of 14:42.
Because these triangles are in a 1:3 proportion, all we have to do to find the area of ABC is divide the area of DEF by 3.
630/3 = 210
The area of ABC is 210 sq. in.
Let me know if you need me to explain anything I did here :))
-T.B.
