start by placing both in slope-intercept form (y=mx+b)
so you have a(y)=-3/4x
and y=4/5x
in order for a system of linear equations to have infinitely many solutions the have to have the same slope and intercept, right now
-3/4 \(\neq\)4/5
so we have to figure what "a" needs to equal in order form the lines to be the same.
so (-3/4)/x=4/5
solve for x
x=(4/5)*(-3/4)
x=-3/5
so we know that "A' is going to be the reciprical of x**
A=-5/3
**how we decided X and why we know that x= the recipricle
so ay=-3/4x
so it would end up being y= ((-3/4)/a)x
and dividing by a fraction is the same as multiplying by its reciprical.