For an 'm-ary' tree the number of nodes n, internal nodes $i$ and leaf nodes $l$
below equation holds
$n=mi+1$..........(1)
and
$i+l=mi+1$.........(2)
The Y-axis represents the number of leaf nodes and the X-axis represents the number of internal nodes
Slope of line=$tan(75.964)=4$(Rounded to nearest integer)
Equation of line $y=mx+c$
can be rewritten as
$l=4i+1$
Subsituting this in (2)
$i+4i+1=mi+1$
$5i=mi$
$m=5$
It's a 5-ary tree.