If y varies directly with x and y=60 when x =15 find k and write an equation of direct variation

large crystals result from very slow cooling.

evaporation of water: this would produce an evaporite which is a sedimentary rock. like a salt pan in a desert. not possible to have volcanic rocks originate this way.

crystalization in molten earth: slow cooling over time. (hundreds to millions of years)

crystalization at earth's surface: this results in fast cooling. (a few hours to a few months or years)

crystalization from cooling off hot water: that would be a hydrothermal deposit. while associated with volcanics they are not volcanic rocks themselves and usually occur fairly rapidly.

credit scoring calculations, such as the fico score, look at a few key factors related to your debt. the amount of overall debt you carry, the ratio of your credit card balances to your credit limit (also called credit utilization), and the relation of your loan balances to the original loan amount.