SAT Subject Test Mathematics Level 1

Figure  1

So a = 1.5, and the answer is (A).

SLOPE-INTERCEPT FORM

With the topic of slope-intercept form, we move from coordinate geometry
that is primarily geometric into coordinate geometry that is primarily
algebraic. Slopes and intercepts are descriptions of lines and points on the
grid, but the processes of finding and using slopes and intercepts are
generally algebraic processes. There’s no need, for instance, to sketch a
diagram for a question like Example 3.

SLOPE-INTERCEPT FORM

For any equation    in  the form    y   =   mx  +   b:

m   =   slope

b   =   y-intercept