The equations are already arranged in a manner that the unknowns can be solved <i>directly</i> by forward substitution (3s=30 => s=something, 2k+s=20 => 2k=something => k=something,...). I am shocked that so many people in that twitter thread are not able to solve them.<p><i></i>Edit.<i></i> But this may be a trick question, because in the last equation, what you have is not a pair of shoes, but one single shoe. The same for the thingy wrapped in newspaper.