K is equal to -69.5 K=69.5 You put it in an equation 47.9-K=-21.6Then you subtract 47.9 from both sides and you get K=69.5
If you're asking how, here's an example
A standard form equation is when it is set up.
Ax + By = C.
6x + 2y = 4.
A slope-intercept form equation is when it is set up y=mx+b.
Y = - 3x + 2.
4y = -8x + 16 then divide all by 4.
y = -2x + 4 slope form.