Year 8 Interactive Maths - Second Edition

Equations Involving Two or More Operations

Example 8

Solve 7x + 4 = 25.

Solution:

The number 4 is furthest away from x.  The inverse of + 4 is – 4.  So, subtract 4 from both sides.

Problem Solving 2

Example 9

If three times a number, when diminished by 4, equals 17, what is the number?

Solution:

Let x be the number.
Three times x is 3x, and diminishing this by 4 gives 3x – 4, which we are told equals 17.

So, the number is 7.