Minimum temperature on Wednesday was ${30}^{\mathrm{o}}\mathrm{C}$. On Thursday, minimum temperature fell by $4^{\mathrm{o}}\mathrm{C}$. Rainfall on Friday caused the minimum temperature to fall further by $7^{\mathrm{o}}\mathrm{C}$. What was the minimum temperature on Friday?

In an Off Season Sale, a shopkeeper makes a profit of $₹50$ on sale of one shirt and a loss of $₹20$ on sale of a pair of pants. Find the number of shirts sold by him, if the total profit made by him is $₹820$ and the number of pants sold is $4$.

During a $12$-hour period, the temperature which dropped by a fixed value every hour declined ${36}^{\mathrm{o}}\mathrm{C}$. How many degrees did the temperature drop each hour?

An insect climbs $2 \mathrm{cm}$ up a slippery rod in one second and slips down by $1 \mathrm{cm}$ over the next second. How many seconds will the insect take to reach the top of the rod $15 \mathrm{cm}$ high?