Susan was posting gifts to her family. She weighed three envelopes before posting them. Geace Envelope A Envelope B Envelope C • Envelope A weighed x grams. Envelope B was 50 grams lighter than Envelope A. • Envelope C was three times as heavy as Envelope A. If the total weight of the three envelopes was 840 grams, write an equation in x and solve it to find the weight of Envelope A. (