Expressions in algebra consist of constants and variables. A CONSTANT is a quantity whose value remains the same throughout a particular problem. A VARIABLE is a quantity whose value is free to vary.There are two kinds of constants-fixed and arbitrary. Numbers such as 7, -3, 1/2, and p are examples of FIXED constants. Their values never change. In 5x + 7 = 0, the numbers 0, 5, and 7, are fixed constants. ARBITRARY constants can be assigned different values for different problems. Arbitrary constants are indicated by letters-quite often letters at the beginning of the alphabet such as a, b, c, and d. In ax+b=0,.the letters a and b represent arbitrary constants. The form ax t b – 0 represent many linear equations. If we give a and b particular values, say a – 5 and b = 7, then these constants become fixed, for this particular problem, and the equation becomes

5x t 7 = 0

A variable may have one value or it may have many values in a dlscuseion. The letters at the end of the alphabet, such as x, y, z, and w, usually are used to represent variables. In 5x + 7, the letter x is the variable. If x = 1, then

and so on for as many values of x as we desire to select.and so on for as many values of x as we desire to select.

If the expression 5x + 7 is set equal to some particular number, say -23, then the resulting equality

5x + 7 = -23

holds true for just one value of x. The value is -6, since

5(-6) + 7 = -23

In an algebraic expression, terms that contain a variable are called VARIABLE TERMS. Terms that do not contain a variable are CONSTANT TERMS. The expression 5x + 7 contains one variable term and one constant term. The variable term is 5x, while 7 is the constant term. In ax + b, ax is the variable term and b is the constant term.

A variable term often is designated by naming the variable it contains. In 5x + 7, 5x is the x-term. In ax + by, ax is the x-term, while by is the y-term.

NO ONE is going to do your homework for you. Solving the first one for your info..

12 +3(4+x) = 12+12+3x = 3x+24

Now get off ur lazy back and do the rest yourself

12+12+3x=3x+24

15+6x+6=6x+21

10+4x+4-5=4x+9

12+6x-9+4=6x+7

18+10x-5+3=10x+16