Use the distributive property to expand the multiplication:
#color(blue)2(p+1)=color(red)3(p-1)#
#color(blue)2*p+color(blue)2*1=color(red)3*p-color(red)3*1#
#2p+2=3p-3#
#2p+2color(blue)+color(blue)3=3p-3color(blue)+color(blue)3#
#2p+2color(blue)+color(blue)3=3pcolor(red)cancelcolor(black)(color(black)-3color(blue)+color(blue)3)#
#2p+2color(blue)+color(blue)3=3p#
#2p+5=3p#
#2p+5color(blue)-color(blue)(2p)=3pcolor(blue)-color(blue)(2p)#
#color(red)cancelcolor(black)(2p)+5color(red)cancelcolor(blue)(color(blue)-color(blue)(2p))=3pcolor(blue)-color(blue)(2p)#
#5=3pcolor(blue)-color(blue)(2p)#
#5=p#
#p=5#
That's the solution. Hope this helped!