Draw x and y axes with a point on the y axis marked to represent 130 and a point on the x axis to represent 30. Draw a horizontal line parallel to the x axis through y=130.
Plot y=4.9x-4.2 by marking the y intercept -4.2 (when x=0) and x intercept 6/7 (when y=0). Join the intercepts and continue the line until it intersects the line y=130. Drop a perpendicular from the intersection to meet the x axis. This value of x is the solution to the given equation. You should find that x=27.4 approximately.