Anumber b minus 4.2 is less than -7.5 an inequality is?

Solve this system of equations. 12x − 18y = 27 4x − 6y = 10

A33 gram sample of a substance that's used to detect explosives has a k-value of 0.1473. n = noekt no = initial mass (at time t = 0) n = mass at time t k = a positive constant that depends on the substance itself and on the units used to measure time t = time, in days

We just started the introduction into circles and i have no idea how to do this.