Equations, unknown numbers and factors

Write an expression for “7 more than 3 times a number n”, and find its value when n = 2.5.

Solve 2.75 + a = 6.

Solve 7 × b = 5.6.

A baker puts 12 rolls on each tray and bakes 84 rolls. Write an equation with t for the number of trays and solve it.

List all the factors of 28 and of 45.