We have 2 triangles.
Large triangle:
Height= x
Lenght = 7
Small Triangle:
Height= 3
Lenght= 4
If we multiply any of the measures of the small triangle by the scale factor, we obtain the measure of the large triangle:
4 (scale factor) = 7
Solve for the scale factor:
scale factor = 7/4
Scale factor = 1.75
Multiply the height of the smaller triangle by the scale factor;
3 x 1.75 = 5.25 ft
Becky's Height = 5.25 ft