A function will not have any repeating x values....it can have repeating y values, but all the x values have to be different for it to be a function.
A is a function because all the x values are a different number
B is not a function because u have repeating x values...u have repeating 4's and repeating 9's
Since triangle DEF = triangle JKL, m<D = m<J, m<E = m<K, m<F = m<L.
m<F = m<L = 90 degrees
m<K = m<E = 5(m<D)
but m<E + m<D = 90 degrees [right angled triangle]
5(m<D) + m<D = 90 degrees
6(m<D) = 90 degrees
m<D = 90 / 6 = 15 degrees.