Make a ratio, then cross multiply.
4/30=x/48
30x=4x48
30x=192
x=6.4
The horizontal value in a pair of coordinates: how far along the point is. The X Coordinate is always written first in an ordered pair of coordinates (x,y), such as (12,5). In this example, the value "12" is the X Coordinate. Also called "Abscissa"
It is a straight angle because it is on a straight line.
Hope this helps :)