Just set up a proportion (that's 2 ratios equated)
1 inch : 30 yards :: 4 inches : x
Notice a couple of things. Inches are on top of each ratio. yards are on on the bottom, although that is not stated with the x.
The x will have a number on the other side of the equation along with the unit of yards.
[tex] \dfrac{1{inch}}{30{yards}}=\dfrac{4 inches}{x} [/tex] Cross multiply
1 inch * x = 30 yards * 4 inches. Divide by 1 inch
x = 30 yards * 4 inches / 1 inch
x = 120 yards
