Make r the subject of the formula: 1/r -1/p = 1/t
- Take the 1/p to the other side of the equation1/r = 1/t + 1/p2) Add the fractions together by making the denominators the same1/r = (p+t)/pt3) Cross multiple by multiplying each side of the equation by the other side’s denominatorpt = r(p+t)4) Divide both sides by (p+t)pt/(p+t) = r
