Ihave problem in calculating mrs (marginal rate of substitution) from mu(marginal utility). explain with example ?

In the figure below, ∠dec ≅ ∠dce, ∠b ≅ ∠f, and segment df is congruent to segment bd. point c is the point of intersection between segment ag and segment bd, while point e is the point of intersection between segment ag and segment df. the figure shows a polygon comprised of three triangles, abc, dec, and gfe. prove δabc ≅ δgfe.

Yvaries inversely as x. y =12 when x=5. find y when x=4

How many doughnuts are equal to 20 cookies.? 3 apples = 5 bananas6 cookies = 7 apples2 doughnuts = 1 banana