CD is congruent to XY, DA is congruent to YZ and AC is congruent to ZX even tho i'm not able to see properly your image
Assuming that CB is tangent, this is just a right triangle with a hypotenuse of 20 and a side of 12 so by the Pythagorean Theorem:
20^2=12^2+x^2
400=144+x^2
x^2=400-144
x^2=256
x=16
The equivalent expression -
4n + 19
100cm is equivalent to 1m so 500cm is equivalent to 5m. What you need to do is divide 500cm (5metres) by 25cm (one quarter of a metre). So the number sentence using 'division' should look like 500cm divided by 25cm which equals 20. Don't forget to use proper symbols for division though. Let me know if this helps:)