The work done in bringing  three particles each of mass 10gm from large distance to the vertices of an equilateral triangle of side 10cm is (approximately)

m=10g=10×10-3kg=10-2kg r=10cm=10×10-2m=10-1m W=−ΔU=-Uf-Ui=-Uf-0(∵Potential energy at inifinity =0 for all the three particles) Wnet=-Uf1+Uf2+Uf3=-2U=−−3Gm1m2r=3Gm2r=3×6.67×10-11×10-2210-1=20.01×10-14J=2×10-13J