Greg,

If two lines are perpendicular, their slopes are negative reciprocals of each other.

The y=2x+3 has slope __________? So the slope "m" of the line you are looking for will be what (see above)

The same x-intercept as x+3y+10. (*)

The x-intercept is the value of x for which y = 0. Set y = 0 in (*) and find this.

Find the equation of this line. Express your answer in the form of y=mx+b.

You know m and the x-intercept (x value for which y=0) and slope; you need the y-intercept "b". So set y=0, plug in m and the x-intercept value, and solve.

Good Hunting!
-RD