Question

For a consumer to be equilibrium why must marginal rate of substitution be equal to the ratio of prices of two goods?

Answer 1

bcoz v need tangency of budget line to the IC for maximising utility, n for that, slopes of both must b equal i.e.
MRS(slope of IC)=P1/P2(slope of budget line)

Answer 2

In order to maximize utility this condition must be satisfied... and as you know more is better for consumer..