a) h(x+y)+(m+n)(x+y) ( expand 1st )

hx + hy + mx + my + nx +ny (group all the x and y variable together)

hx + mx + nx + hy + my + ny ( factor out x and y )

x(h + m + n)+y(h + m + n)

(x + y)(h + m + n)

c) x2 - 8x - 20 ( Just factorise )

(x-10)(x+2)

Hope you can do qn d by now