Cd = dc x + 13= 13 + x
4 (2x - 3) = 4 (2) - 4(3)
2+(a +b) = (2+a) + b
Please help me I will give brainliest, thanks and a lot of points

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.