Here's one way.
pd2 = makedist('Normal','mu',2,'sigma',0.2); pd3 = makedist('Normal','mu',3,'sigma',0.3); pd5 = makedist('Normal','mu',5,'sigma',0.5);
x = 0 : 0.001 : 10;
y = 0.2*pdf(pd2,x) + 0.3*pdf(pd3,x) + 0.5*pdf(pd5,x);
figure plot(x,y)
It requires the Statistics and Machine Learning Toolbox.
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