Expand and simplify (x-5)(3x+3)

Begin by expanding brackets using FOIL (first, outer, inner, last) method (demonstrated on whiteboard to make clear). Multiplying the first term of each bracket gives 3x², multiplying outer terms gives 3x, multiplying the inner terms gives -5x, and multiplying the last term of each bracket gives -15. Therefore we have 3x²+3x-5x-15. Collecting like terms and simplifying gives us 3x²-2x-15.