For any linear equation, the general structure of the standard form is:
Ax+By=C
Where both x and y terms are on the left side of the equation and the constant is on the rigth side.
If you have a variable in slope-intercept form, to transform it to standard form you have to pass the x term to the rigth side, for example:
For the equation y=10x+30 the standard form is -10x+y=30